Can it be added to any thread post not just for Clans?

As far as I know you can't pin, what ever msg is the latest goes on top :o/ That has been complained about but not likely to be changed. The formated is twitter/Facebook, not keen on it myself for a message board, but the powers that be decided to do it this way (shrug). Have to work with what is available, who knows may/not change in the future.

If you mean threads on the boards, then yes you can edit your own messages but not others.