There's a sub to test if you are shadowbanned. The mods set it up so automod automatically approves any post there, so that way even if you're shadowbanned you can post.

Then a bot goes through and scans to check your comments and sees if they show up.

When shadowbanned, people can still see your comments if they go onto your profile. They just won't see it in the thread.

You ever seen a thread that says something like "3 comments" and you click and only see 1? 2 people commented that were shadowbanned.

I've gone through the sub and browsed through profiles of people who were shadowbanned. Some of them posted nothing controversial to warrant a shadowban.