Not actual teal world examples, but many variations exist. "lol so drunk when I wrote this", "Ed has so many, many issues", "tumblr style tags ftw".

Their purpose is to convey the artistic vision of the fanwork as commentary, and I find them very useful to my fannish experience, since it's been quite helpful in avoiding particular works, as the author pov is one I will likely not identify with.

Tag wranglers currently deal with them by assigning to a fandom if applicable and not canonising or marking unwrangable if applicable. (so they don't clog sidebar /drop down)

if a tag is not a character, fandom or relationship, there should be multiple uses before canonising - so for example if a group of people started tagging with "get xxx laid challenge" in order to group works for a particular challenge - that could get canonised.