There are qualified doctors, as well as almost qualified doctors who frequent H&R too and give advice.
If TSR is getting professionals to work on here as professionals, (as Fiona is doing), then I think she needs some sort of disclaimer in her signature and she needs to be quite careful. As you say, we don't know enough to categorically diagnose anyone over the internet and it's generally considered unprofessional to do so.
Which is why as yet she hasn't posted in the public forums.