Specifically a rule banning it so we don’t get defederated, coupled with a clarification about what it means to fall under this category.
I’m thinking of situations like characters that look underage but canonically aren’t (i.e. the 1000 year old loli trope) and characters that are drawn indistinguishably from adults but are canonically underage.
Here’s a picture of Jotaro Kujo cosplaying as a Diglet, who was 17 at the time.
Doesn’t look at all as your typical 17 year old but then againi it’s JoJo.
All I’m saying that it can be sometimes difficult to distinguish what is ok and what isn’t but I’m in favour of not having anything underage anywhere on the internet.