Some days ago, I added a couple of empty links on my user page. They showed, so I enclosed them in <nowiki> so that they would be passed through as HTML and be invisible. I just checked and they are visible. Was something changed?
Well, it's either broken or fixed, depending on your point of view. I was convinced by requests in the bug tracker that the "right" thing to do was not parse HTML inside nowiki blocks. If you want to hide something on your user page, put it in HTML comments: <!-- like this --> (and comments can't span lines, BTW).