Another option (though far more work than the admins probably want to do; this is pie-in-the-sky here) would be to expand the thread-tag system to include a lot more topics (as in dozens if not hundreds) in some sort of macro-tag micro-tag system and then make it such that each thread would have - or could have added to it by the admins - multiple tags. Ignoring a micro-tag catches just those threads while leaving the rest of the macro-tag available.
So, for example, NuTSR might get its own micro-tag under the WotC and-or TSR macro-tags; and someone could choose to ignore that "NuTSR" tag while still seeing other threads under the WotC and TSR macro-tags. Under each of the D&D-related macro-tags (e.g. "D&D General", "5e2024", etc.) might come micro-tags for "Rules Questions", "Players", "DM Advice", "Edition Conversion", "Design Ideas", etc.; thus someone who isn't interested in edition conversion could ignore that micro-tag and it'd block all threads with that micro-tag regardless of which macro-tag they're under.