Thread:Forum:Tech Wishlist And Bug Reports/Watchlist/reply (3)

Above. It's a new feature which was added in MediaWiki 1.23 to make things more social. I don't think I noted that to community - my fault :p

On a side note - IIRC it can be disabled by default for the wiki if Geth or labster wanted it to be, they can poke me and I'll see what I can do :)