And it never will, because having some way to identify a message is a prerequisite for even phrasing the question "does device_foo have message_x synced yet?"

Bouncers don't count. They reintroduce centralization as a way to solve the problem. It's a solution, of a sort, but it's a fairly poor one if your original aim was decentralization.

And "working fine" is also frankly a bit of a stretch, isn't it? I can't count how many times I've seen a "netsplit" in freenode or the other IRC networks. That means messages aren't delivered. It's so common we have a word for it: "netsplit".

I shouldn't dunk on IRC too much, because at least it's honest about itself for being simple, and there's a virtue in that. But if we were to construct a statement like "IRC manages reliable message delivery without any concept of message IDs", then that would be false (or technically, vacuous), because it doesn't manage reliable message delivery.