A while ago I committed to the Chemistry stack exchange proposal. I already had an account on physics.stackexchange.com, and I intended to commit using that account, but instead I ended up committed as an "unregistered user". (I don't remember exactly why that happened, but I do remember that the process of committing was pretty confusing. There was a box saying "real name" and I was like "huh, that'a bit weird, but I guess at some point it will ask me to log in to my account and my real name won't be published", but no, it just published my real name and created a new account-that's-not-an-account-because-you-can't-log-into-it.)
Anyway, I later decided to fix this by un-committing and then committing again using my existing account. But the problem is, because I committed as an "unregistered user" I didn't seem to have an account I could log in to in order to un-commit. So how can one either delete an "unregistered user" commitment, or associate it with an existing Stack Exchange account?
Update: This specific situation was resolved by one of the Chemistry.SE mods merging the two accounts. (I think I asked on their meta as well. This was a while ago now, and Chemistry.SE is now in beta.) However, the more general question about how an unregistered user can manage their account and commitments remains unresolved.