Ask yourself this question; Would we allow all posters to do this? Can every poster insert “This is my stupid catch-phrase” into every post they submit? We’re not talking about signatures - he’s putting it in every post.
If you let Snowboarder Bo get away with it you’re setting a precedent.
May I now put “OASIS IS THE BEST BAND EVER!!!” in every single post I make?
Can every single poster on this board do the same? If it’s OK for Snowboarder Bo, it has to be OK for everyone.