For the reasons :
Discourse has a lot of sugar and settings that the competition doesn’t really have, or not as clean.
StackOverflow is great but doesn’t provide its soft, or too expensively (>=$175k).
For the dev :
Sorting out the posts via JS seems easy, but side effects happen on the right side chrono-elevator.
(I’am first thinking about a dirty client-side JS solution)
The “Reply” form, also, suggest a flat system.