The thing is, the discussion *was* had several years ago. See the thread entitled "Single login - decision 2004" on foundation-l. And it seems that most people discussing it there, including Erik, Jimbo, Jamesday, Kate, and Daniel Mayer, said that they'd prefer not to rename any accounts.
Angela and Ant commented that they'd like for there to be a poll. AFAIK there never was such a poll.
You can't do it without renaming accounts. It would be pointless. Why have a single account per person if they all have different names? It's not really even a single account, since accounts are pretty much defined by their names (yes, there is a numerical id in the database, but only developers care about it - and I don't think that id would be the same anyway).
You can only have a poll if there are multiple options. Edit counts is the only option I've seen anyone propose that stands a chance of working.