I questioned what you said I didn't (when I asked you) state that the poster wasn't his mother. I don't know that she is or isn't.
That said I will now say that I feel that it's highly unlikely that a mother who has lost her son to suicide is going to open up a HN account [1] and post something when a loss like this happens.
Of course if a HN admin has access to IP addresses or where and how the account was setup or some other non public information that's something else.
How do you know the person who setup that account and posted that is actually his mom?