Honestly, like they said, even coming from a place of concern, it’s not ok.
Nobody is about to get their first insight into having a mental health condition like an eating disorder from comments on porn that they’ve posted. It’s just not a reality. Anybody who gets those comments online has already heard it all before, and knows how people feel about it.
I would say, if somebody is actively promoting an unhealthy lifestyle by glorifying bulimia or undereating, then it’s a good time to speak up so others aren’t influenced, and to make it clear that promoting those things can lead to serious mental health issues.
Telling someone they should gain weight, lose weight, get a boob job, go to the gym, stop going to the gym - it’s all totally inappropriate, and potentially very damaging.
Nobody is getting their first insight into having a mental health condition from comments they read on porn they’ve posted. There are enough social connections in most people’s lives for them to have heard it all before.
If somebody is actively promoting practises that are damaging to mental health, then it’s reasonable to speak up so other viewers don’t think it’s good. If they’re not, they almost certainly have a much clearer view of the situation than a commenter seeing their pictures online.