On my user page on my home wiki, I am trying to hide everything with Hidden Comments markers, but it doesn't seem to be working very well.
It's because you're using –, or –, as opposed to -, commony found to the right of the 0 and the same key that contains an underscore. Whilst they do look rather similar, html is picky about it.
I noticed you've used the correct format just after the original use. Using nested comments like this
<!--comment 1<!--comment 2-->comment 3 -->
Ends up looking like:
Because the closing --> on comment 2 closes the first comment. Just use -- or something else instead.
Instead of hiding everything on your Profile page, why not take the stuff you're wanting to hide to your sandbox. Profile pages are most often only used to tell a bit about yourself. All the "useful info" type of stuff you can put in your sand box.
What do you think?