Imagine this scenario:
someone (X) asks a question (Q) in #C0922A726;
someone else (Y) provides an answer (A);
a third man sees that, and marks question Q with a special emoji
a bot reacts to the emoji and sends a DM to X , asking him to post his question Q on SO
X posts Q on SO, then pings the author of the answer A to post A to SO
bingo!