I think you are being too strict about closing question just because the answers might include legal advice and that advice might come from non-lawyers. As with all answers here, there is no absolute guarantee they are correct. Should only those with a PE license be allowed to answer engineering questions? Of course not. Answering legal questions is no different.
The second question you link to (What is an engineer's liability for code changes that occur after submitting a design?) is a good example. I found the answers to be generally well written, apparently written by people that knew what they were talking about, informative, and quite interesting. Of course I understand these aren't official legal advice, and "But your honor, it said on Stack Exchange that ..." isn't going to work.
Give us some credit for being able to evaluate the quality and validity of information we get here, just like we do everywhere else in life. This is no different than talking to other engineers around the office water cooler. Nobody is going to take that as definative rulings, but the conversation can be interesting and enlightening nonetheless. Answers here are actually better because more people will see it and the peer-review process is more likely to catch errors. Also, people's personal experiences can be useful to hear, even though they are just single examples suffering from sample size. Again, that's my business, not yours, to judge.
So in short, let's lose the nanny-attitude. If people feel comfortable answering, let them. Let others take that for whatever they think it's worth. We shouldn't be getting in the way of that as long as the discussion still relates to engineering or issues real engineers regularly face in real situations.