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.
The coward’s way: don’t explain why you did what you did clearly, just obfuscate/point towards some “guideline”. 🙄
Not even a guideline, just some guy’s personal opinion.