I've never put any stock in this point, your writings cannot be made distinct from you.
How many messages do you need before you can accrue enough personally identifying information to reveal who that person was? Every time they mention where they live, how old they are, what happens about that?
None of that goes away if you only soft delete the user's profile, leaving all the content and context for anyone to rebuild at their leisure.
Pretty sure the original account id is still tied to the message and sent to clients even after deletion. People can easily correlate it if they can prove just one of the messages belonged to you.
How many messages do you need before you can accrue enough personally identifying information to reveal who that person was? Every time they mention where they live, how old they are, what happens about that?
None of that goes away if you only soft delete the user's profile, leaving all the content and context for anyone to rebuild at their leisure.