Mods should be able to pre-emptively ban a malcious account from all communities that they moderate, not just the community that was attacked.
I thought they could. I once got banned from several generative-AI art comms for posting in the FuckAI comm. Kinda wish the person had reached out as my position on AI is neither extreme nor set in stone, and I quite liked some of the things posted in their comms. I would have loved to have had a discussion. Anyway, the ban ended up only being for a week or two. I've made sure to upvote some stuff they posted, but I shouldn't really need to do that.
From title, I disagree with you because I browse /all pretty exclusively, but I sub to a bunch of comms I think are interesting. I just haven't gone to /subscribed or whatever yet, because the Fediverse is growing and new stuff is being added all the time and I wouldn't want to miss out, and it's small enough I can keep doing this.