That does not stop chronic multiple replying posters, it really only annoys customers that have a need to post multiple replies in a quick fashion for one reason or another.
Which is endemic on a (non-Xenforo) writing forum that I frequent. The only place I have found the delay an issue is on my own site when I am rapidly jumping between forum games.
Why is another reply considered spam? Hmmm I usually reply to my own posts if I need to add info. It's easy to reply again and then you are sure it is seen because they may have already read the post you edited.
Do you mean because users care about post count? To me that is a legacy concern. But then again these are moderator preferences and you can moderate this forum how you like.