@Ernest Bywater
Yes, if you follow that style.
Technically, an aside is NOT a complete sentence, so you really can't add a question, though I can see why you'd want to, especially for 1st person 4th wall scene (where you're directly addressing the reader), but it's still not valid.
On the other hand, I frequently aside in parentheses (or more accurately an aside ending in a question), but only here in the forum, where readers won't think I'm a complete moron (since the authors on the Authors Forum already know that for a fact).
In short, it's fun to break the rules like that, but there's really NO context where it's correct. But then, if you're already breaking the 4th wall, obviously you don't mind breaking form.
I avoid em dashes like the plague as they do not render correctly in every web page or every e-book reader, and when the render bad they really mess up the text.
I have no idea which browser you're using, as I've NEVER had a problem with using em-dashes. The key is that browser engines are who powers the html in most eBooks, so they SHOULD always display correctly.
Thus, I'm not sure whether you're using an ancient system, or whether it's an inherent Linux flaw (Linux browser behavior maybe?). Though, if you post your SOL files using text, then the em-dashes will NEVER work, simply because that an exclusively html function.