I can see why this would be useful. I like pinup type art, and if a Mature type rating ever gets implemented I would bump my settings to allow it. However, there are some things that I don't want to see M/A art of that I like clean art of, such as fanart of a favorite TV show or videogame. Allowing us to block tags for certain ratings would allow me to block, say, mature Undertale art while still allowing me to see the clean Undertale art without having to forgo the pretty pinups.

Us prudes that don't want to be buried in an avalanche of dong but still like certain artists' styles would appreciate this :3

Endless scrolling seems cool and all until everything slows to a crawl because you're 20,000px down the page and Chrome has consumed all the RAM, murdering your hard drive with excessive swapping because you just want to catch up on the last couple of days' posts. The site seems to unload images that go off the top of the page but that doesn't stop browsers from rendering the 18,000px of mostly empty space.