Working with the RadContextMenu that comes from the RadRichTextBoxUI, when having analytics enabled, produces a NullReferenceException.

Manually set the Menu property on the PreviewMouseLeftButtonUp event of the RadMenuItem:

static MainWindow()
{
    EventManager.RegisterClassHandler(typeof(RadMenuItem), PreviewMouseLeftButtonUpEvent, new MouseButtonEventHandler(OnRadMenuItemPreviewMouseLeftButtonUp), true);
}

private static void OnRadMenuItemPreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    RadMenuItem radMenuItem = (RadMenuItem)sender;

    RadContextMenu radContextMenu = radMenuItem.ParentOfType<RadContextMenu>();

    if (radContextMenu != null)
    {
        PropertyInfo menuPropertyInfo = radMenuItem.GetType().GetProperty("Menu", BindingFlags.Public | BindingFlags.Instance);
        if (menuPropertyInfo != null)
        {
            MethodInfo setMethod = menuPropertyInfo.GetSetMethod(true);
            if (setMethod != null)
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    setMethod.Invoke(radMenuItem, new object[] { radContextMenu });
                }), System.Windows.Threading.DispatcherPriority.Background);
            }
        }
    }
}

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.

Implement child dialogs for Style Formatting Properties Dialog. This will allow users to modify Style's properties related to font properties, paragraph properties, tabs, numbering and borders.