I see... right now only one comment delimiter is supported in our LineBaseLineCommenter class. You might be able to override that class and its Uncomment method, and call the base method. If that ends up changing anything, I think the "snapshot.Document.CurrentSnapshot" would no longer be the "snapshot". So if the current snapshot remained the same, no change was made, and you could set the commenter's StartDelimiter property to your alternate delimiter. Then call the base method again. After that restore the StartDelimiter to your primary delimiter. It's a little kludgey but might work with the existing code for your needs.
We also will add a suggestion request for enhancing line commenters to support more than one comment kind.