Such questions then usually get ignored or closed as "unclear", which is not really helpful.
Well, nobody said it is. Unfortunately, the truth is you often can't help these people in any way when it's a (new) user that vanishes till the cows come home. They call some of these "unsalvageable" for a reason.
If someone manages to come by and understand (not guess at, mind you) what the OP is getting at, and take their time and edit the post into shape, it'd be a true form of chivalry! But let's bear in mind that it's the OP's job to post something that's in the best possible form to answer. That's what @Mith is getting at.
A little chivalry goes a long way sometimes, when all the post lacks is a couple of miscapitalized I's or when the message is clear enough. Usually, if I don't have the time or the certainty to edit the question, I'd comment on why it's not necessarily unsalvageable. It's OK for the close voters to do some meta commentary on the post as long as it doesn't clutter it too much, and we all need to get 'em Marshal badges now, don't we? ;)
On the other hand, since you mention "vocabulary", sometimes people are just not familiar enough with the terminology. I saw one recent example (not linking it due to meta effect) with pretty clear English but a poor choice of terms, and these usually fall under the "general reference" I mentioned in my recent post. It's also typically an unfortunate situation, because best case scenario is answerer taking their time to write a perhaps lengthy answer, only to find out it was an XY problem, or a chameleon question, or a myriad of other bad words. The OP should have continued reading their textbook instead of impatiently posting their half-baked question. A no-win situation is best amended with the fast-firing bullets of close votes.
All in all, I do think the experience of such OPs can be greatly improved, but I don't think they're being unfairly treated, and usually, there's no one to help them immediately, not even themselves. I assume the "language flag" you talk about won't be in French/Indian/Martian, so it probably won't solve much ;)