What do I tag images with bad grammar which aren't engrish, such as post #1052523?
Should I just create a bad_grammar tag? After all, we do have a typo tag for another type of mistake.

That would be ranguage.

+1 bad_grammar

why not just imply ranguage -> bad_grammar?

bad_grammar imo is better though, as it justifies itself while not all people know ranguage

I'd assume frandle scarlet falls under ranguage or at least be surprised if it didn't. It certainly doesn't fall under bad grammar.