Looking at it... It looks like the thread was removed, but not deleted. (Deleting is an extra step.) Removing it takes the thread out of the Board listing, and out of RC & Wiki Activity. It's still visible if you follow a link through the Contributions or the board history.
If you delete it -- which is an extra step after removing it -- then the links will still be there in your contributions and the board history, but only admins will be able to view the content of the thread. Does that match up with what you're seeing?