A few weeks ago I used PDS to edit my comments - using the fork with the 5 second delay. Random pockets of older comments started reappearing after few days. I've been checking all 45 pages of my history every few days and editing the random comments that have reverted from the edited message. It seems like it has mostly stuck now.

I guessing there's probably some broken code/process somewhere that isn't always able to commit changes and once caches expire the comment returns.