The line break symbol (Shift+Enter) is treated as a text character and it gets measured in the document position calculations executed when you click at the end of the document (somewhere after the line break symbol which ends the line). 

This causes two visual issues. The first one is that the caret goes after the line break symbol, which means that when ShowFormattingSymbols is False an empty space (non-existing in the document) is added at the end of the line. Even if ShowFormattingSymbols=true and the line break symbol gets display, it is not expected for ,the caret to get positioned after the symbol.

The second issues is that, when you start typing after you click at the end of the line, the caret position is corrected, but this leads to a jumps of the caret with one character to the left, which brings an unpleasant visual glitch.

To work this around, you can create a custom MouseSelectionHandler and override its RegisterDocumentMouseDown method. This will allow you to check if the caret is placed after the line break symbol and manually update the caret position if that is the case.

public class CustomMouseSelectionHandler : MouseSelectionHandler
{
    private IDocumentEditorPresenter presenter;
    private RadDocument document;

    public CustomMouseSelectionHandler(RadDocument document, IDocumentEditorPresenter presenter) 
        : base(document, presenter)
    {
        this.presenter = presenter;
        this.document = document;
    }      

    public override void RegisterDocumentMouseDown(bool ctrlPressed, bool shiftPressed, Point position, UIElement originalSource = null, SourceType source = SourceType.Mouse)
    {
        base.RegisterDocumentMouseDown(ctrlPressed, shiftPressed, position, originalSource, source);
        var box = this.document.CaretPosition.GetCurrentSpanBox();
        if (box != null && box.AssociatedSpan.Text == "¬")
        {
            document.CaretPosition.MoveToCurrentLineEnd();
        }
    }
}

 this.richTextBox.Loaded += (s, args) =>
 {
     var presenter = (DocumentPresenterBase)this.richTextBox.ActiveEditorPresenter;
     presenter.MouseSelectionHandler = new CustomMouseSelectionHandler(this.richTextBox.Document, presenter);
 };

ArgumentException occurs when using the voice typing feature of Windows (started with the Windows Key + H key combo) to convert speech to text in RadRichTextBox.

Exception stacktrace:

System.ArgumentException: 'Requested distance is outside the content of the associated document.'PresentationFramework.dll!System.Windows.Documents.TextPointer.TextPointer(System.Windows.Documents.TextContainer textContainer, int offset, System.Windows.Documents.LogicalDirection direction)
  PresentationFramework.dll!System.Windows.Documents.TextContainer.CreatePointerAtOffset(int offset, System.Windows.Documents.LogicalDirection direction) 
  PresentationFramework.dll!System.Windows.Documents.TextParentUndoUnit.Do() 
  PresentationFramework.dll!MS.Internal.Documents.UndoManager.Redo(int count) 
  PresentationFramework.dll!System.Windows.Documents.TextStore.RedoQuietly(int count)  PresentationFramework.dll!System.Windows.Documents.TextStore.SetFinalDocumentState(MS.Internal.Documents.UndoManager undoManager, System.Collections.Stack imeChangeStack, int appChangeCount, int imeSelectionAnchorOffset, int imeSelectionMovingOffset, int appSelectionAnchorOffset, int appSelectionMovingOffset)  PresentationFramework.dll!System.Windows.Documents.TextStore.HandleCompositionEvents(int previousUndoCount)  PresentationFramework.dll!System.Windows.Documents.TextStore.GrantLockWorker(MS.Win32.UnsafeNativeMethods.LockFlags flags)   PresentationFramework.dll!System.Windows.Documents.TextStore.RequestLock(MS.Win32.UnsafeNativeMethods.LockFlags flags, out int hrSession)

FormatException is thrown during the import of a table coming from a docx document when the application culture is "sv-SE". This happens when the column width in the document is a floating point number (ex: 120.65). The Swedish culture uses "," as decimal separator and " " as the number group separator, which makes any invariant decimal value (like 120.65) invalid during standard parsing (ex: float.Parse("120.65")).

Stacktrace:

FormatException: The input string '4514.5' was not in the correct format.
at System.Single.Parse(String s)
Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.TableImporter.ImportTableGrid(Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Parsing.Style style)  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.TableImporter.Import(Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Parsing.Style parentStyle)  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.MainDocumentImporter.BuildTable(Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Parsing.Style parentStyle)  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.MainDocumentImporter.BuildBody()  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.MainDocumentImporter.BuildDocument()  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.MainDocumentImporter.Import()Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.DocxImporter.ReadXmlContentFromPackage(Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.DocxPartImporterBase importer)  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.DocxImporter.ReadXmlContentAndRelationsFromPackage(Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.DocxPartImporterBase importer)
Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.Import.DocxImporter.Import()  Telerik.Windows.Controls.RichTextBox.dll!Telerik.Windows.Documents.FormatProviders.OpenXml.Docx.DocxFormatProvider.Import(System.IO.Stream input) 

To work this around, switch to InvariantCulture during the import and return the original culture after that.

 var cultureCache = Thread.CurrentThread.CurrentCulture;
 Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.InvariantCulture;
 Thread.CurrentThread.CurrentUICulture = System.Globalization.CultureInfo.InvariantCulture;
 var provider= new DocxFormatProvider();
 rtb.Document = provider.Import(stream);
 Thread.CurrentThread.CurrentCulture = cultureCache;
 Thread.CurrentThread.CurrentUICulture = cultureCache;

RichTextBox: Bullet list with several levels is not viewed correctly in WordPad. 

In Word, this works as expected. When the document is imported into RadRichTextBox, this works as well.

Bold/Italic does not work for some font styles.

This might be a framework limitation in WPF: https://www.telerik.com/forums/some-fonts-are-not-able-to-bold-italic

Sample fonts list:

1. Tw Cen MT Condensed Extra Bold (bold/italic)
   
2. Tw Cen MT Condensed (bold/italic)
   
3. Sitka Text Semibold (italic)
   
4. Sitka Subheading Semibold (italic)
   
5. Sitka Small Semibold (italic)
   
6. Sitka Heading Semibold (italic)
   
7. Sitka Display Semibold (italic)
   
8. Sitka Banner Semibold (italic)
   
9. Segoe UI Variable Text Semibold (italic)
   
10. Segoe UI Variable Text Light (bold/italic)
    
11. Segoe UI Variable Display Light (bold/italic)
    
12. Segoe UI Semilight (bold/italic)
    
13. Segoe UI Semibold (bold/italic)
    
14. Segoe UI Light (bold/italic)
    
15. Segoe UI Black (italic)
    
16. Script MT Bold (bold/italic)
    
17. Rockwell Condensed (bold/italic)
    
18. Rockwell Extra Bold (italic)
    
19. Rage Italic (bold/italic)
    
20. OCR A Extended (bold/italic)
    
21. Nirmala UI Semilight (bold/italic)
    
22. Microsoft YaHei UI Light (bold/italic)
    
23. Microsoft YaHei Light (bold/italic)
    
24. Microsoft JhengHei UI Light (bold/italic)
    
25. Microsoft JhengHei Light (bold/italic)
    
26. Malgun Gothic Semilight (bold/italic)
    
27. Leelawadee UI Semilight (bold/italic)
    
28. Gloucester MT Extra Condensed (bold/italic)
    
29. Gill Sans Ultra Bold Condensed (bold/italic)
    
30. Gill Sans Ultra Bold (bold/italic)
    
31. Gill Sans MT Ext Condensed Bold (bold/italic)
    
32. Gill Sans MT Condensed (bold/italic)
    
33. Franklin Gothic Medium Cond (bold/italic)
    
34. Franklin Gothic Heavy (bold/italic)
    
35. Franklin Gothic Medium (bold/italic)
    
36. Franklin Gothic Demi (bold/italic)
    
37. Franklin Gothic Demi Cond (bold/italic)
    
38. Franklin Gothic Book (bold/italic)
    
39. Dubai Medium (bold/italic)
    
40. Dubai Light (bold/italic)
    
41. Corbel Light (bold/italic)
    
42. Copperplate Gothic Light (bold/italic)
    
43. Copperplate Gothic Bold (bold/italic)
    
44. Cooper Black (bold/italic)
    
45. Cascadia Mono SemiLight (bold/italic)
    
46. Cascadia Mono SemiBold (italic)
    
47. Cascadia Mono Light (bold/italic)
    
48. Cascadia Code SemiLight (bold/italic)
    
49. Cascadia Mono ExtraLight (bold/italic)
    
50. Cascadia Code SemiBold (italic)
    
51. Cascadia Code Light (bold/italic)
    
52. Cascadia Code ExtraLight (bold/italic)
    
53. Candara Light (bold/italic)
    
54. Calibri Light (bold/italic)
    
55. Britannic Bold (bold/italic)
    
56. Bodoni MT Condensed (bold/italic)
    
57. Bodoni MT Black (italic)
    
58. Bernard MT Condensed (bold/italic)
    
59. Bahnschrift SemiLight Condensed (bold/italic)
    
60. Bahnschrift SemiLight SemiConde (bold/italic)
    
61. Bahnschrift SemiLight (bold/italic)
    
62. Bahnschrift SemiBold (bold/italic)
    
63. Bahnschrift SemiBold SemiConden (bold/italic)
    
64. Bahnschrift SemiCondensed (bold/italic)
    
65. Bahnschrift SemiBold Condensed (bold/italic)
    
66. Bahnschrift Light Condensed (bold/italic)
    
67. Bahnschrift Light  (bold/italic)
    
68. Bahnschrift Condensed (bold/italic)
    
69. Arial Rounded MT Bold (bold/italic)
    
70. Arial Narrow (bold/italic)
    
71. Arial Black (italic)

Currently, the only customization that can be performed is using HyperlinkToolTipFormatString property of RadRichTextBox, which sets the format for all hyperlinks in the document of the control. It would be nice if it were possible to be able to set different tooltips. 

It seems that the first time a Center TextAlignment is applied to the selection, its length is cached. Because of this, when the selection content (text) changes the length is not updated, thus the text doesn't align properly. It aligns accord to the initial length of the context. The content doesn't update also if the alignment is reset.

To work this around, avoid the FlowNoWrap layout mode and use only Flow.