If it's only downvotes, then a ban is justified.

Ask your community members, maybe?

I lean towards "go for it! block away" but I come from a different internet culture than reddit so could never mod anywhere similar. You might get better advice from someone who's spent more time in these spaces.

To me, It seems like chronic downvotes from nonmembers could mess up your comm's discovery. And is mildly annoying. Not terrible, but I don't think they need to be evil to get a community block. If you do it too much, your community might stagnate and people might start a new one. Oh well! Good luck to the new guys, imo. You might end up on PTB and get harassed. Always a risk as a mod, unfortunately.

Put "frequent exclusive downvotes from non-members gets a block to increase likelihood of community discovery by people interested in this content" on your profile. I mean, if you talk with your community members and they agree it's an issue.

Is it possible they're a bot?

~~It’s not possible to see unless you’re an admin or use some ActivityPub service that federates with Lemmy but doesn’t hide this information from the end user.~~

That is to say, I would if I could, if there was a malicious pattern. I didn’t understand the outrage that Reddit wanted to do that too (although their ruleset and ways of enforcement are not my cup of tea).

In the meantime, lead by example and refrain from downvoting unless for rule breaking content or offtopic so that toxicity doesn’t increase.

I'd say just ban them. Doesn't look like a healthy relationship for either side. Worst thing that can happen is they complain and you get to know the reason for their behaviour... And if they're under the impression it will get rid of the posts, banning them will accomplish that, so win-win.

If it's everything (in a community/profile) maybe, particularly if they don't have any contributions elsewhere. Or if it's actually something heartfelt/personal I can see being more touchy about it, less so with bot-like aggregation or reposting old content etc.

Because otherwise, it's not going to be obvious where the line is when you add in time and % of content. If you're using a bot/script to detect voting, you're likely going to ban users just for casual browsing (even if they could explain their votes). Especially as an instance ban purges a user's account (to users of that instance) as if they're on the same level as an SEO spammer. Does a voting disagreement mean the rest of their account is invalid?

I don't know if it's fedi incompatibility or just 0-transparency moderation, but dubvee might be doing this but it's unclear as they seem to be just handing out silent bans (no ban reason stated).

PTB?