Edit: apparently not. See below.
~~I've been following the status of my own reddit profiles since I deleted my contributions on Monday & Tuesday of this week. I used a browser script to download and then edit my comments, and upon a second pass to delete them. I operated primarily on two accounts I still hold.
Today I, like many of you, was surprised to see a lot of my original, unedited comments back on my accounts. After several hours I re-ran the browser edit/delete cycle and upon review found more unedited and undeleted comments, yet no revived posts from the last pass. This piqued my curiousity. If there had been a restore, it seemed incomplete and it missed my submitted content.
My day continued: check in on the profiles, edit and then delete some posts, go outside a minute. I began noticing a pattern, that new crops of zombie posts would occur on both accounts at the same time, and were always from the same subreddits. I would delete them, and they seem to be staying deleted. I have yet to delete any one comment twice that I have noted, and I am looking.
Those are my observations. As to my theory, I think if you manipulated comments of you're on a subreddit while it was locked or restricted, that those changes are cached until the subreddit unlocks. At some point either caches got flushed, changes timed out, or I was getting to my own content before the cache worker did. (For all I know that worker is some poor, unpaid mod-slave). Anyway, I think the cached changes got lost, and the subs reopening reasserted hidden content.
Tl;dr, It amounts to a protocols nuance on the back end. Pitchforks on standby, this isn't the strawman we were looking for.
Epilogue:
B- b- but solidgrue you fucking apologist, why you defend Reddit so???
I'm not trying to defend reddit, egads no. Reddit is doing some shady shit lately on the PR front. While I wouldn't put restoring deleted content past them, they have lawyers who would have pointed out how EXCEPTIONALLY a bad an idea that would have been. There are compelling arguments under GDPR and the US CDA section 230 regarding ownership and "content provider" that discourage this. Rather, I want to acknowledge that we Rexxitors are leaving, and leaving angrily. Reddit's management is already playing the Us vs. Them angle. It'd be an unforced error on our side to run with the Restored Content angle too hard when it's a mundanely reddit infrastructure problem.
We'll need credibility when they drop old.reddit.com, and NSFW content from their mobile app~~
(Edits: sloppy editing)
Edit 2: theory refuted. Standing down. I has asked earlier about pre-blackout edits & deletes but got no answers. Now we know.