[yarg]

I'd use a question comma, there are often times where I'll phrase a question and then expound on some deeper specifics - generally things that I would consider implied, but that many people would miss, leading to the misinterpretation of the question.

Essentially everything (for me, at least) after the question comma is generally parenthetic in nature.

[yarg]

Are you sure you want to do that? You're going to break your legs.

Having thought a bit about it, I'd say it's the question version of a semi-colon.

[paxys]

All the examples of question comma on the site can easily be written as two sentences though.

[yarg]

And most sentences with a semi-colon could also; it's often a matter of personal preference without well-defined fixed rules.

[dragonwriter]

> And most sentences with a semi-colon could also

Well, yeah, since the difference between a comma and a semi-colon is the latter joins independent clauses, it is necessarily the case that any semi-colon use for joining (as opposed to its use in, e.g., lists) can be replaced by a period, you just lose the indication that the two independent clauses are tightly associated.

[pasquinelli]

a question mark doesn't have to end a sentence. such a question mark is often used to separate a succession of questions that all elaborate one idea. it used to be more common, but i know as recently as 1991 ursula le guin used it in the story "Texts", ("Whatever those eleven years had been, the length of a marriage? a child's life? they were gone"...)

most of those marks only have any cause to exist at all because people are so stuffy about punctuation, unless you wrote "The Dispossessed."