I have "-votedup:me" for my blacklist entries and "voteddown:anything" as its own entry (so things I upvote should be exceptions, and things I downvote should be blocked, in theory). But they don't do anything, and I think I remember being told before that the site just doesn't support that. But I would appreciate if it did.

Yes, the site does not support that. And that's unlikely to change in the near future.
The site currently does not store the information on whether or not you voted on a post in a way that can be easily retrieved without running into performance issues.

I would still like some way to blacklist/whitelist posts on a post-by-post basis.

Like, there's some tags that have specific posts that I find really gross, but don't have any specific blacklistable tags.

And there's some posts with blacklisted tags that are okay in context that the tags can't really differentiate, such as violence for story reasons rather than being fetishized. (Hell, even one of my OWN posts was on my blacklist because of this until I added a "-fav:me -lendri_mujina" modifier to most entries.)

But, I'm not sure how else that could be done.

lendrimujina said:
I would still like some way to blacklist/whitelist posts on a post-by-post basis.

You can blacklist individual posts, you just put in the list as so:
id:<post ID here>

hygiene said:
You can blacklist individual posts, you just put in the list as so:
id:<post ID here>

Okay, thanks.

hygiene said:
You can blacklist individual posts, you just put in the list as so:
id:<post ID here>

And you can append another id to the same line by adding , and the next id, something like id:637421,5000001
Edit: Wait what this is supported for post search but not blacklists?

snpthecat said:
And you can append another id to the same line by adding , and the next id, something like id:637421,5000001
Edit: Wait what this is supported for post search but not blacklists?

The blacklist never supported that syntax. Seems a little annoying to implement, to be honest with you.
Especially since you can just put id:637421, id:5000001 on multiple lines.