Before I left Reddit, I used a plugin through the api to replace all of my comments with random gibberish and then delete them. Part of this was because (mandatory) fuck spez. But more importantly, it was to protect the anonymity of my account. After years of posting, there is likely enough personal information shared to potentially connect my Reddit habits to my online identity. I wasn’t planning on using Reddit again in the future on that account, but I left it open in order to maintain some security control over the account. I’m not really sure what to do at this point because I still consider it a security vector that’s a bit concerning. There’s no way I can manually edit and delete all of my content with the snail’s-pace reddit UI, and I have no ability to assure that my content will remain unavailable or at least not publicly displayed.
There might be something to this. I went and checked just now, prompted by a your comment, and I found a handful (like, six) comments from ages ago on reddit that did not get torched when I did my mass edit-and-delete, somehow. I found these mostly because some punters found them and necroposted on those threads, so I have notifications regarding them.
I found a few more and deleted those by hand, too. Most of them were from the same sub, so that sub was probably locked when I did my mass delete.