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.
Yes and no, respectively.
It's wrong in the same way that DRM is wrong.
Am I alone in this?