Seems to me the best way to implement the "login-as" feature is to make it possible for an admin account with sufficient privileges to just enter the name of an

Seems to me the best way to implement the "login-as" feature is to make it possible for an admin account with sufficient privileges to just enter the name of any user to start a "nested session" from their admin account (password of the user you're logging in as not required) where they see everything the real user would see but the logging somehow remembers that this is a nested session. So you could differentiate between RandomGuy actually logging in, Hexstream logging in as RandomGuy and MetaNull logging as RandomGuy. No need to fuck with passwords, guys!