Actually, I want them to post but I don't want it to appear as separate post.
Sometimes, user forgets to include something and they remember after they click post reply. And my users are not really good with such stuff and instead of edit they simple go for next post !!
I could solve this thing, but merging double post..
If you have a regular database then you could educate them with PM's or via a thread discussing why they shouldnt do it. You will find after a while they will start correcting each other.