The mod banning these users is the same mod who made the posts they downvoted. This is mod abuse, turning the downvote button into an auto-self-ban button.
The message is “If you disagree with me, you will be banned”
Monitoring and banning users for using lemmy as intended to signal boost your opinion should be grounds to have all mod privileges removed. This behaviour undermines the integrity of the server and the wider fediverse.
Well that would mean a lot of attention seeking troll posts could trend.
Depends on how exactly it’s implemented, sure. That obviously isn’t the result I’d be looking for.
My point, though, is only that a “downvote” need not mean “hide this kind of post away from the general public”. A downvote can mean something more like “This pissed me off and more people should read it.”