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.
Your position is reasonable if down votes are suppressive, but I wouldn’t develop a content algorithm that treated them as such.
I would use an “engagement” algorithm. Upvoting increases engagement, commenting increases engagement, down voting increases engagement, reporting increases engagement. The viewing time - the time between initially accessing it and viewing a new page - increases engagement.
The most suppressive thing you can do to a piece of content is click away in less than 20 seconds.
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.”