On a similar note, copying the password to the clipboard is the weakest link in the usage of password managers today. Everything that is running on your system has access to your clipboard content and even get notified when you copy something to it.
Your tool of choice should have an option to generate easy to read/write passphrases and you should prefer those whenever possible (without weakening the password itself), so that you can avoid moving your passwords to the clipboard whenever possible.
I hate a lot of the things that reddit has been doing but I still think not all of them are on purpose. I ran into this issue myself before it was widely discussed and my first thought was that it had simply failed to delete some comments or deleted only from some cache.
So far every exampe I've seen of this can still be explained by bad engineering and I see no reason to think it is "undeleting" stuff by design, since it seems to happen to very random content that has no general value (like restoring 20 random comments out of 900 that were deleted).