It seems that very recently the "Tag Blacklist" feature just stopped working. Nothing is blacklisted, even though I have 71 tags blacklisted. I visited this site a few hours ago and everything was fine. I don't know if this is a bug or what.
EDIT: Never mind, it's working now, don't know what that was all about.
EDIT2: I think I found the cause of this problem. Whenever I click the "Having issues with your blacklist saving? Click here" button the "Tag Blacklist" feature stops working until I log out and log in again.

Yes. That button completely deletes your blacklist cookie. It'll stay deleted until you either save your blacklist again or log in again, at which time the site will set your blacklist cookie again.

The blacklist is entirely run from your browser cookies. We store a copy on the site, but it is not used to control your blacklist; it's only there so you can have the same blacklist across multiple devices. Instead, we store a copy of the blacklist in your browser, which is sent to the site each time you request a page. That is what we use for blacklisting, and since it's stored in your browser, you can manually change it or delete it in your browser and it'll use those changes rather than what we have stored on the site.