So the artist Dacad was banned for the reason "Please tag young on images that have characters that are very clearly young coded," for trying to remove the young tag from https://e621.net/posts/4573337?q=rigby_%28regular_show%29 which is his own art. Despite Rigby being small and thin in it I can't see any other visible indication he's supposed to be young or young looking.
Now I know the tag what you see system is and how it works, it's simple and it can be very useful. However in this case the artist is telling you how it's supposed to be tagged and the visual indication that supports the use of the "young" tags is shaky at best.
Updated by Donovan DMC