Sorry but the points are totally valid. If you delete your account your messages are still available with a userid that if someone has it can be traced back to you. They also don't delete files or pictures you uploaded alone for this they should get fined.
isn't that the case for gmail? if you send me an email with a picture in it, then delete your email account, i can still see your email when logging into my gmail
If you send email to me and then delete it in your end, I'm allowed to store your email as a whole (sometimes legally obliged).