Speaking generally: remember that there’s a difference between general medical/legal advice and specific cases. It’s perfectly OK to discuss “What are some diseases that cause blurry vision?” That’s very different from “What causes MY blurry vision?” In both law and medicine, the individual symptoms and situations play a critical role. If you go to a doctor and say, “I have blurry vision,” she will ask you a whole string of questions (including what medications you’re taking, family history, etc) that you didn’t mention in your online question. A doctor will also (one hopes) notice that you’re having trouble breathing, a symptom that you didn’t mention in your thread. Thus, we’re OK with discussion of general medical themes, but we’re uneasy when it’s being applied to an individual case.
Similarly with legal questions: individual circumstances can make a big difference. We’re perfectly OK with people discussion general themes (“what does the law say”) but we’re uneasy with people applying the law in their situation.
I don’t think we’d have any problem with your hypothetical, “I’ve already discussed this with my doctor, she’s at a loss, anyone have any suggestions that I can give her?” You’d be asking for general suggestions, not your specific case, and you’re working with a doctor.
Yes, our focus is on medical and legal and any other profession where U.S. law requires some sort of registration or licensing (accounting and actuarial topics are similar, among others.) When it comes to things like auto repair, carpentry, plumbing, computer malfunctions… well, we’re more open to allowing discussion. I think someone almost always comes into such threads to say, “Consult with a professional. Online advice, you often get exactly what you pay for.” I note that the “hammer a bullet” thread that you linked to, most posters say, “This is a bad idea.” I presume you’d get the same result with, “I think I have heart palpitations, how can I perform a bypass on myself?”
And, finally, what Rico said: if you see someone getting/giving advice that you think is dangerous, by all means: post in that thread to say that you think it’s dangerous, and alert the mods by reporting the post (li’l exclamation point in red triangle in upper right corner of post.)
That answer your question?