...is how they're displayed, with 1 being the original post. Now, what actually happened was...
1 (original post)
2 (reply to thread)
3 (reply to thread)
4 (reply to 2)
5 (reply to 4)
6 (reply to 3)
7 (reply to thread)
8 (reply to 6
9 (reply to thread)
10 (reply to 1)
... users do the generic "Reply to This Topic" at the bottom, while others click Reply on the bottom of a specific post of interest. So, what I'd expect multiquote to do if my hypothesis holds is display the quotes in this order...
...because what we really have is...
...if we were using an outline view. Now, as far as I know, locals don't have a way to tell if a given post is a general reply or a reply to a specific earlier post, so I don't have a way to test this without making a thread and replying to myself A LOT. Which I'm totally going to do in one of the testing forums, because if my hypothesis holds then I'm a genius.
EDIT: And my hypothesis did not hold up to testing. Here's what I got when doing exactly the scenario described above:
This is a multiquote selecting posts in 1-2-3-4-5-6-7-8-9-10 order.