There are some people I'd like to follow who regularly post content I really don't want to see. They are all very good about tagging it, so, it would be nice if I could just not see those posts from those users!
(Muting a tag generally would also be a useful feature, but would not solve this use case at all.)
It's a bit niche but now that I think about it it makes a lot of sense. A way to specify a tag/user combination that you don't want to see would fill in a lot of weak spots of tag based mute systems.
Oftentimes people end up making a tag like "#[theirusername][triggering thing]", but I think that solution misses the case you're looking to resolve here as such a post would also be tagged with "#[triggering thing]" if the person is using such tags correctly
This would be especially useful with an expiration timer (mute for 7 days etc) so that when someone hyperfixates on something but it will probably pass, I can opt out of the hyperfixation just for now and still see other content with that tag in the meantime
As someone who is very annoying, I would appreciate giving people the ability to filter me.
This came up in the little sidebar search while I was making this request for following a specific tag. It's distinct enough that I think they should be separate requests, but I figured people interested in this might be interested in that, too.