Unless the comment itself identifies you in some way, removing the connection to your user profile renders it no longer personal data.
The reason other platforms may decide to simply delete everything when you ask are: 1. they don't care about your old stuff; 2. they don't want to spend time checking individual cases. So they pick the cheapest option.
You have to be veeeeeeeeeery sure that the commend didn't contain any personal data though. Just because somebody submitted it willingly doesn't mean you get to keep it.
It could be done with a non-advanced non-AI for decades. E.g. by metrics like vocabulary and simple markov statistics.
You don’t expect posts to be deleted on request. Because e.g. the internet archives will still contain them and have no way to identify you to “comply”. There’s privacy in labels, but not in essence. Just accept it.
Unless the comment itself identifies you in some way, removing the connection to your user profile renders it no longer personal data.
The reason other platforms may decide to simply delete everything when you ask are: 1. they don't care about your old stuff; 2. they don't want to spend time checking individual cases. So they pick the cheapest option.