Crosswicking your own work, as long as it's available publicly, should be just fine.
As for YMMV, however, adding subjective tropes to your own work's subpages isn't allowed; creators are biased in how they see the work, and thus detached from the audience, whose opinions we're documenting.
Current Project: Incorruptible Pure PurenessAs long as you can write objectively about your own (admittedly that's difficult) work you should be fine
New theme music also a boxYou can do Trivia as well, but these items must be *externally verifiable* (like posted about elsewhere), not just things you intended to do for the work. For example, if you personally hate Alice but that's just your personal feelings and you've never mentioned it on, say, a blog post or in author notes, you can't add Creator's Pest.
The only thing you're allowed to do for YMMV is change factually incorrect information (like an entry says "Alice is 14" but she is actually 16.) By definition, the creator is not the *audience*.
Question in title, pretty much. Can you get away with this, or do they not allow it? What other things can you do regarding your own work on this site? YMMV pages, for example?