I personally do not think that this is a very good idea.
Let's say there are two users debating about something and no moderators are on. One user will make a post, and the other user will have to wait however many hours just for a moderator to accept the post, and then the other user will have to go through the same process. Seems like a total pain in the neck and ruins the flow of conversation. Now, you could technically debate in a private conversation, but then all other people viewing the thread lose out on whatever points were brought up for and against whatever they are debating against. It would literally hurt the flow of information from user to user.
Another scenario, is that many users are on, and no moderators are on. Let's say somebody says something controversial, and a bunch of people disagree. One person voices their opinion against the post, but no moderator is on to accept the post. Then, another user sees nobody has voiced their opinion against the controversial post and does the same. 3 hours and 50 posts later moderators are stuck with a bunch of posts that literally say the same thing. The harder part? They have to decide which post to accept and which ones to decline, because there is no use saying the same thing 50 times.
TL;DR, this suggestion would just make the forums clunky to use.
Also I'm a little curious, why make this suggestion? I understand suggestions are suggestions and there are no bad ideas, but you literally joined today and have a single post. If anybody were to make this suggestion, I feel like it should (or at least would) come from somebody who is more used to using the forums.