Regular moderators can effectively shadowban inside their subreddits by using AutoModerator and telling it to remove all posts made by certain users. While your comment makes it sound like AutoMod just removes comments, what I think you're meaning to point out is that AutoMod can selectively hide all of a user's comments to everyone except for the comment author, which is the exact same as shadowbanning, and isn't just a simple comment removal. A lot of subreddits use this feature now, too. Some automatically shadowban any user that doesn't have above a certain amount of karma, while others auto shadowban everyone and then only maintain a whitelist of authorized posters. If you've ever posted on a subreddit and gotten zero replies/votes, it's worth going into incognito mode and trying to view your comment from there. Chances are, your account is shadowbanned in that subreddit.