That could win me over! I'm not sure what the appropriate answer is to "who should it put in the committer line?" (especially if author and committer are already different), but that's not a huge problem, I don't think.
It would be a problem for me - suddenly, my local branch and the Github branch are no longer in sync, and I have to untangle this mess before continuing development. (And if I don't notice that Sedy is changing the revision history, and only realize it when I've made a couple of commits and try to push...)