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.
While that was the intent of upvote/downvote in some places early on, virtually nobody has actually done that to a sufficient degree for it to not be agree/disagree.
I guess I’m one of those old dinosaur users that still tries and mostly adheres to that old unwritten rule but the lines of inflammatory BS, rampant strawman, whatboutism with disagreements has made it so much harder.