Next time, thanks to this thread I'll do nothing. I now understand why people don't speak up, because they get blamed for the whole thing.
Just wow. What an odd response. The whole time reading the thread I was thinking that you handled it perfectly with regards to your daughter and the other child, and then this. Which sadly makes me realise you're not as well equipped to handle issues of this nature as you believe you are.
You handled the situation fine. But the entire thread, as a whole, your tone comes across very much as 'isn't my DD amazing? She's such a star! She handled it so well. So did I. We're great' without barely any compassion for the actual child in such a dark place she's self harming.
Your reference to 'DD isn't into this sort of thing' I.e. Having poor mental health, self harming, was crass.
I think that is what is getting people's backs up. You actually asked 'AIBU to be shocked?' Some said yes you are, and explained more about it from their own perspective. Others said no, it is shocking to them too. You got your answer. But I'm not sure what the point was of the rest of the thread other than wanting a pat on the back for how well you and DD handled the situation.
Which you got. And now you say:
Next time, thanks to this thread I'll do nothing. I now understand why people don't speak up, because they get blamed for the whole thing.
So next time you come to realise a friend of your DD's (use the term 'friend' loosely at that age, based on them having shared their personal details and communicating outside of school) is self harming or may be desperate for help, thanks to your defensiveness at answers on an anonymous message board from unrelated anonymous adults you'll choose to do nothing. Despite being very pleased with yourself for how you handled it this time.
That is bizarre, and horrifying.