It'd be great if there was a tag for posts containing characters who are underage in their source material cause like... I don't wanna see that :/

There's already loli shota tag

That doesn't seem to stop Misty, Raven, Gwen, Azula and a bunch more from showing up

That's because people age them up to where they're not underage.

At that point I'd just blacklist those kinds of characters instead.

Besides, isn't Raven an adult in the comics?

As was mentioned, just blacklist specific characters. We’re not going to create a special tag just for this. And if you have any questions or suggestions about tags, please take it to the Official Tags thread next time.