Are questions from non-professional historians allowed?
By this, I mean questions that may seem obvious to a professional, but not necessarily to a layperson.
I think all the questions on the site are from history enthusiasts (read: non professionals) and I wouldn't be surprised if that was the case for most of the answers as well. I'd say it's safe to say that questions from amateurs are allowed and more often than not, enthusiastically welcomed.
That said, as T.E.D. noted, we do expect questions to show at least some amount of prior research. We really don't want a site that's full of obvious answers, that would get extremely boring very fast. However it's extremely difficult to define a common baseline for the amount of prior research required. Each and every one of us has different standards, expectations and skills.
How do we maintain sanity, then? Well, that's easy, by combining our different standards, expectations and skills. It takes five votes from high(ish) rep users to close a question (i.e. deem it unsuitable), one or even four persons' opinions don't really mean much. I'd go as far as say that if you don't agree with one person's opinion of your question, you can just ignore it, at least until it becomes obvious what the community's opinion is. There's one notable exception, the people with diamonds next to their usernames; they are moderators exactly because we trust them to single handedly do stuff.
Although I don't think I'm in any way a representative user, just to give you an example, my workflow for determining prior research is a five minute search. I take the more important keywords from the question, enter them into Google and:
I'm guessing everyone has their own workflow, and I should note that (obviously) my workflow only applies to questions that aren't a mess to begin with. I wouldn't spend five minutes on rants (in disguise or not), extremely trivial questions and questions in broken English (on these, my five minutes are better spent in editing the question).
Both your questions pass my "five minute test". Obviously, the Australia one didn't pass someone else's equivalent test, but that's both understandable and expected. Some people on the site will be a lot more familiar with certain areas than others, and will be able to dig up relevant information and possibly the answer almost instantly. So what, as I've already mentioned, you shouldn't lose any sleep over what one person thinks.
Also, if you ignore the condescending tone of the comments, what remains is that someone familiar with the subject matter of your question answered it, almost immediately. I agree they could have been a bit nicer about it, but at the end of the day you found the information you were looking for. That's not so bad, is it?
Of course, I'm not suggesting that the ends justify the means. The comments, although not outright rude, weren't particularly helpful and you could have just flagged them. Or, just ignore them. But saying that "I do not think I will be able to write to the standards this site requires without getting an abrupt and condescending comment" is an overreaction. I'd strongly advise against letting a single bad experience shape your opinion of the site, especially since you have found at least some value on the site (more specifically, the answer to your other question).
Stick around, and give the site another chance. Keep in mind that it's extremely tough to convey emotion in comments. The person at the other end of the line might just be tired, or having a bad day, or whatever, and they screwed up with their comment. Or you might just be misinterpreting the comments. It doesn't matter, whatever the reason for a not so friendly comment, if it's just one (or even two), just ignore it.
About the only time I see questions getting closed for being too simple is when they are something that could easily be answered by hitting the subject's wikipedia site and reading the contents therin.
You are expected to make some small attempt at research on your own before asking. At least enough to perhaps link to the wikipedia site in question and explain why the contents don't answer it for you.
For example, in the case of the comment you got on https://history.stackexchange.com/questions/9113/was-there-a-plan-by-axis-powers-to-completely-navally-blockade-australia-in-ww2#question, a good response would be to read the wikipedia material for Australia in WW2 and explain why that didn't enlighten you (assuming it didn't).
What we are trying to avoid is answers that are basically just a single naked link to wikipedia. A website full of those wouldn't be of much use to anyone.
With that in mind, I deleted the offending question, and upon reflection saw that the one I had before it (about ancient city planning) was as bad. Looking at it, the question about Arabic trade routes is also bad as it does not include a Wikipedia reference.
But, I do not think I will be able to write to the standards this site requires without getting an abrupt and condescending comment.