I’m not sure if it’s a coincidence, but I raised a case with the ICO in the UK, and today they got back to me asking for all my communication with Reddit. Also today - after a month of silence - Reddit also emailed me with this
If you’re in the UK and had been affected by posts being restored, I’d recommend contacting the ICO. It takes less than 5 minutes
Okay, now that’s a plausible explanation. Some of those subs may have been private and coming back online over several days. Thanks for the insight.