I did not have a specific editor in mind however
markdownsharp is a c# implementation that I would consider my preference.
I note that the textarea of the forums uses a markdown syntax, so I'm not sure what implementation supports it.
The use case I am considering is allowing content editors the option of entering content using a markdown syntax instead of plaintext or FCKEditor's WYSIWYG interface.
This would be similar to Wikipedia or StackOverflow in that the user is in a WYSIWYM (what you see is what you mean) mode.
I'm new to Kentico development so I'm just curious if anyone has implemented something like this already.