I might be wrong, but I think most of those issues were from people trying to edit comments that were in a subreddit that had gone private. I don’t think the API could deal with that.
The first time I did it, a bunch of my comments were still there. I did it again, and after that it seems like all of mine have stayed edited (but I’m not going to check thoroughly, there were a lot)
That’s not a spoon, this is a spoon!