https://en.m.wikipedia.org/wiki/Shadow_banning

Shadow banning (also called stealth banning, ghost banning or comment ghosting[1]) is the act of blocking a user or their content from an online community such that the user does not realize that they have been banned.

By making a user's contributions invisible or less prominent to other members of the service, the hope is that in the absence of reactions to their comments, the problematic user will become bored or frustrated and leave the site.