In a game, I posted as a GM that a fight had just started, I'd rolled Spot and two characters got to act in the surprise round.  In the post I also said what the attacker was doing.

Two minutes later a PC posted -- apparently the PC post was started before I'd posted and it went through after mine did.  Yes, there's that "a post was made" but the player thought it was from asynchronous player posting.  It would be great if there was a way to bump a post sooner into the thread.  Perhaps, if that happens, change the post date to read, "Bumped" or something?

That is not possible with the way RPoL stores the threads.  Every post has a number, which never changes, and is used by the system to determine what order posts appear when displaying the thread.  So your post would always appear before the player's post.

The easy way to fix it would be for the player to actually pay attention to the warning, and look at what was posted, or for you to delete your post and repost it after the player.

Posts are displayed in numerical order.  Bumping a post would require reordering all the post numbers, and though that's programmatically possible, it would mess up any links and/or "In reply to..." messages.

Though it clearly would have some purpose, I think it'd largely be niche.

As GM, I have (very rarely) copied a player's post when it was chronologically inconvenient, then deleted the post, and re-posted the content as the player after my GM post. Be sure to lock the thread while you're doing so to prevent any intervening posts.

I've done the same with both my own posts and those of other players. I'm generally pretty relaxed about it and try to tweak that only if the player is OK with it.