Thread:TK-999/@comment-5175866-20130511222154/@comment-5454372-20130515183014

Hey Superdadsuper, I believe you'll find what you're looking for by navigating to Special:AllMessages.

For the "Community Corner has been updated" message specifically, it should be at the following location on your wiki:

You'll need to have admin rights to edit that though. As for other pop-up messages, I'm guessing you'll have to find those individually in the MediaWiki namespace...