How would people know if there's a game breaking bug that wipes your save file if they don't get a indication via a new post symbol if it automatically merges with the previous one?
To round-house kick this question quickly, I've seen this double post-merging thing-a-majig in action before. It only merges your posts during a certain time-limit. Like when you edit your post after just posting it. If you're quick, you won't get the "edited by" thing. Same here. If you post quickly after posting once then it'll get merged. If you post after say.... 15 minutes and you had another post before the new one, then it won't get merged. All about the timing.

At least that's how it works on that other forum. And it's also vBulletin, just like this one.