Not the same as a ban
A subreddit ban is local. You get a message, and the rest of Reddit still works. A suspension locks the account and tells you. A removal deletes one comment and usually tells you which rule. A shadowban is quiet, which is why people keep posting into it for days.
What tends to trigger it
New accounts that post the same link in several subs, vote rings, and behavior that looks like a bot. A single removed comment does not mean this. A profile that disappears to logged-out users does.
Stop posting the moment the logged-out check fails. Appealing from the same pattern, faster, makes it worse. The check and the longer recovery notes are on the shadowban tool page and the main guide.