What is shadow banning?
You send a post thinking it went through but it was actually blocked.
Article on shadow banning on vice.com https://news.vice.com/amp/en_us/article/43paqq/twitter-is-shadow-banning-prominent-republicans-like-the-rnc-chair-and-trump-jrs-spokesman?__twitter_impression=truer
Shadow banning (also called stealth banning, ghost banning or comment ghosting) is the act of blocking a user or their content from an online community such that it will not be readily apparent to the user that they have been banned.
By making a user's contributions invisible or less prominent to other members of the service, a hope may be that in the absence of reactions to their comments, the problematic or otherwise out of favor user will become bored or frustrated and leave the site.