@teotwaki Oh I strongly believe there's a UX issue but it's not from hastags:
I believe it's from Mastodon's almost total lack of tools for the wider audience to signal bad behavior.
There are technical ways this manifests (cross-instance weirdness), but even when all things are working as intended, new replies end up in the bottom. Which means people can be assholes to posters with nobody else seeing that occur to push back on it.
That seems to have gotten better but it's not gone.