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.