For things that look legit, for example seasonal political campaigns, and include in message something like “reply STOP to quit”, replying “STOP” does usually end it quickly. Recommended.
Should be one of the first things any anti-spam app/feature should be doing. Wish it was automated into OS spam defenses, then the “responsive human” worry would be eliminated.
I used Power Delete Suite (javascript IIRC, via Firefox, year ago) to edit and delete, and mine are still gone. Not sure if it is still effective.
Reddit is probably less and less tolerant about edits and deletions, now that they’re full speed on selling our data. Still see plenty of deleted posts when I’m searching for things, which is… nice I guess (bittersweet).