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.
Piefed has keyword filters that can help with that issue.
Keywords filters are really basic. Most people don’t want to bother with that, or risk hiding interesting posts
I filtered “musk”, “trump”, reduced the amount of US politics post tremendously
I might add “kirk” at some point, depending how much it’s still discussed in the coming weeks