Did they re-appear after you had remembered deleting them, or were they just not fetched when you looked the first time? I think Cassandra might be to blame where it returned a bunch of wall posts but not all of them when you looked back in history the first time.
This too! I've seen in happen as well in my quest to delete a couple years ago.
The UX is useless by design to make it really hard to bulk delete, the backend is shitty and you can't see your content on friend's walls that disabled their account.
It is bad to the point that you wonder if it is on purpose. My guess is that it is. "Shitty product" as a deterrent to deletion.
Try building a scalable database to billions of users on ad revenue and make it retrieve all data from years ago within the time constraints that users want to see newsfeed items in, you'll see ;)
I must have deleted over 10k things, so there's no chance of remembering whether they were on the list of things I deleted or simply didn't appear.
I mostly used the Activity Log (button at the top of your profile page) to do the deletion. There are filters there so you can see the different types of interactions. Removing them is different, e.g. Delete vs Unlike.
During the process, I did notice things appearing which had previously not appeared, so that definitely does happen. I kept going back to see if there was new stuff to delete. The whole process took me about 3 months.
The plot twist is that this all happened over 6 months ago. My profile has been empty the whole time, until sometime within the past couple of weeks, where posts have started to re-appear.
