The flagbot would be a good idea, but you need to be careful I feel when downvoting people, especially where they're non-English speakers trying to comment on an "English" post. Being too heavy-handed, especially with new users will only serve to drive away the potential growth of the platform.
Having said that, for the worst offenders, and those who continue to spam, the flagbot could add their name to a global blacklist, which could stop the upvote button appearing next to their comment.
Maybe something to suggest to utopian-io??
I made a comment about that. I had that problem and it's sad.
Well I call it a flagbot, but calling it a flagtool would’ve been more accurate I suppose. It would preferably still involve a manner of manual curation / input. The main goal being able to flag with lower than 1% (if applicable) as opposed to any kind of autoflagging
@blacklist-a does this. Flags from @sneak invoke @blacklist-a, and apparently a horde of upvote bots then will not upvote your posts. While you could inquire for more details about how this works, I think this is a covert program, and have had to piece together this much information about it from various sources.