> I don't consider something that remember the login URL for a site (which most password managers can store) a marginal improvement at all.

Me neither, that's why I proposed a system that will allow your password manager to log you in automatically with a single click instead, with a trivial change to the server (a file with some information).

> I'm saying we should make better systems (not perfect ones) easier to use.

Having seen how little adoption Persona, which was pretty much perfect, got, I don't think the problem is usability.