I looked at XKit a while ago, but it seemed total overkill for just wanting a blacklist, like one of these things that reconfigure everything in Tumblr, plus its instructions warned against conflicts with Stylish and Greasemonkey... but desperate times and all, so I disabled the nonworking Tumblr Savior and that Tublrh8te greasemonkey script that let you vanish individual posts and I installed XKit and its Blacklist extension. And it works! It still seems a bit like using a giant Rube Goldberg machine just to have a blacklist effect at the end, but whatever. :D