I kinda gave my thoughts in the Discord, but I'm on the side of leaving the double posting rules how they are. I get that it can be a little inconvenient, but I think that the current system is the best way to go since it's broad and applies everywhere. Adding exceptions is always messy because it's harder to explain, enforce, and understand.
The current rule allows thread creators to double post as long as 24 hours have passed since their last post. I think that maybe adding a bit to extend this to other hosts and not just the original creator could be a good idea, but in most cases it works fine to have the limit be 24 hours. The reason that this was originally brought up was because the host of a tournament (Wheegalure) wanted to double post with the results of a battle without having to edit it into the post where he announced the matchups. I can get the reasoning for wanting to make a separate post, but realistically it's not hard to just do something like this to accomplish the same thing without a new post being needed:
Main Post bla bla bla
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[EDIT] New information
The only situation where I think a double post is the most warranted is if some sort of new important information needs to be added, but in the context where nobody else has posted yet I think that those situations are already iffy. If 24 hours haven't passed yet, it's likely that others haven't seen the thread/update, and if you're still the most recent poster people it'll still be the most recent thing in the thread when someone else does view it. If it's been a substantial amount of time since the first post and you're worried people will miss the information, waiting a little longer to meet the 24 hour requirement is a realistic solution too.
There might be some situations where that isn't true, but I don't think that these situations are a big enough issue that we need to make the double posting rule more complicated. If it's really that important, you can use other workarounds like having someone else post, or bringing up the new information to people directly on Discord or maybe even through private message.
Regarding mentions, editing a ping into a message that's already been posted doesn't send a notification, so unfortunately that's not really a workaround for double posts.
In the end this isn't something that I think will substantially help/hurt the site one way or the other and is mostly preference, so if there's a lot of support to change the rule I think we could modify it in some way. I just think the way things are right now is better.