Hi Bobga Danjuma,
We are very happy that you have chosen to use RadRichTextBox.
The feature you are referring to is currently in our TODO list, but unfortunately we can't give you a specific time frame in which it will be implemented.
The answer to your second question is yes, you can implement this functionality yourself, but I don't think the code from ASP.NET AJAX editor would be compatible with Silverlight.
If you have any other concerns, please contact us again.
the Telerik team
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