With all respect, I think you are somewhat taking your concerns too far.
I have Aspergers which falls under the same label and I feel somewhat offended about reducing it to being "mentally ill" The OP even linked to a wiki article that gave quiet a handful of terms better fitting than "mentally ill". But never mind that one. I don't get where you make the connection from autism to risks of suicide. Yeah in both cases one needs professional help. I can't say much about the professional help one with depression and suicidal intentions would get.
But I can tell you, someone who has a diagnosis and can tell you what kind of autism he has, is very likely aware of the fact of how, or at least that, it influences that person, and probably also is getting or at least got professional help.
I don't know exactly what the thing about PDDNOS is, but just by reading his post, I related to the thoughts he is struggling with and just looking his wiki link up showed that it has connections to Asperger's.
But still I was not sure enough, so I asked for clarification in the comments... That is the usual Stack Exchange procedure, can't see anything worrisome about that.
Also very early on, on this platform, I tried to figure out if we planned to support it (I have Asperger's, is my contribution even gonna help for this private beta?) and my impression so far is that this site is a real magnet for autists.
So, yeah you are right so far, that we need professional help, but not because we are in an unstable state of mind in general, but because we perceive our surroundings differently and need help to get an idea how that's different from the perception of neurotypicals.
For that reason there are tags like asperger or autism. They indicate that here is the source of the question related to our different perceiving hence, if you have no grasp how that might affect the topic, refrain from answering. But not being able to answer is not a reason to default close a post.
And while I somewhat agree on this specific one, that it's a bit opinion-based in its current state, with a bit help to clarify what OP wants to ask it can be a 100% valid question.