Tag filtering is possible on a per-user, per-tag basis for the Reading page of a paid user.

A tutorial post here https://kore.dreamwidth.org/1321059.html takes you through it. I used it for the first time yesterday, although when I followed along I hadn't yet created a Default filter, so I did so, and threw all my currentsubscribe list into it, then added the specific tag from the specific user that I wanted to block.