Originally downvoted this as well as began writing an answer stating I'd rather have the profile page clean without clutter, thinking that for any practical purpose where you'd want to filter a user's posts, you can use the search page. But then I thought, well... once I'm already on the user page, at least a basic set of functionality like sorting, would be nice. So I guess I don't have the answer to this after all.

I wasn't imagining filters on the main profile page (where only the top 15 posts are displayed). I'm only suggesting filters for the page that shows all of a user's posts.

You could have a link to a search page with the filters pre-filled.

Do you mean from the page that shows all of a user's posts?

Or do you mean that instead of having a page that shows all of a user's posts, that could just be a search results page with that user specified as the search term? (So "See all" goes to a search results page rather than a dedicated user's posts page.)

I originally meant the list within the profile, as I didn't realize you were talking about the separate page. But with that brought up, I'm thinking it could perhaps just direct to the search page instead.

As long as it's a separate page, we don't get any of the benefits of still being on the profile page (like on SE). If the list was still shown inline, replacing it with the search page may be a bad idea. But since we don't actually do that, I think it would be better to simply direct there.

If that were an answer, I'd be likely to upvote it.