The "You can't do that now, catch you breath and try again" Messagebox

I'm not just talking about CCing, what buggers me more is the fact whever I try dropping items, this pineappling messagebox had to jump out of nowhere...

I've always wondered about this as well. I guess what they're trying to prevent is you dropping equipment or something that will let a team mate get new equipment ("here, take this adamantium plate to forge a new Dragon Claymore") and then using that to save your ass. I mean, okay, so what? Trading bypasses this, and this will almost never come up unless you're in desperate need of HP equips xD

What doesn't make sense to me is how you can't shuffle around items in your inventory.