Hi Daniel Walton,
We are glad to hear that you have managed to get the ASP Editor working in a Silverlight application.
As for our RadRichTextBox for Silverlight, it does not currently support the snippet-adding feature. You are one of the first customers to inquire about it and currently we do not plan on adding it to our editor.
You can, however, implement it yourself, as RadRichTextBox is fully extensible.
If you have any other questions, do not hesitate to contact us again.
the Telerik team
Browse the videos here>>
to help you get started with RadControls for Silverlight