If RadRichTextBox contains a table and is placed in a window and then the window is resized horizontally, the table border are moved unexpectedly and change their place relative to the content of the documen. If the window is maximized and/or restored, some of the borders disappear.

Workaround: Execute the following code snippet in window's or RadRichTextBox' SizeChanged event handler:
if (this.MyRadRichTextBox.ActiveEditorPresenter != null)
{
    this.MyRadRichTextBox.ActiveEditorPresenter.RecreateUI();
}

NullReferenceException when changing themes, the RichTextBox has TrackChanges enabled, and the current user is set.

Workaround: set empty user like this: 

private void RadRichTextBox_ProtectionStateChanged(object sender, EventArgs e)
{
    if (this.radRichTextBox.CurrentUser == null)
    {
        this.radRichTextBox.CurrentUser = new Telerik.Windows.Documents.Model.UserInfo(string.Empty, string.Empty, string.Empty, string.Empty);
    }
}

Add a way to convert between RadRichTextBox's RadDocument and RadWordsProcessing's RadFlowDocument. 

This will enable integration scenarios between the two products, including using RadWordsProcessing's format providers for import and export.

Text containing mixed Right-to-Left and Left-to-Right parts are visualized incorrectly - some of the punctuation marks swap their places.

Partial workaround: Use RadRichTextBox's TextRenderingMode = TextBlockWithPropertyCaching. This mode also has problems, but it works in some cases.