That is, I think humans can be part of the async system and understand that what they're typing isn't committed yet.
Sometimes when I type I don't even look at the screen or the keyboard for a bit -- entire sentences even. Less so with code, naturally. When I do this I do have to eventually look at what I actually entered, because I might not have noticed some typo, say. I just did that for this entire paragraph. I want to believe that I'd handle speculation in the UI just fine.
“Sorry, there are merge conflicts, please resolve them before resubmitting,” or, “I resolved them without consulting you.”