https://bugzilla.wikimedia.org/show_bug.cgi?id=55190
--- Comment #5 from Kunal Mehta (Legoktm) legoktm.wikipedia@gmail.com --- After thinking even more on this issue, even for those not using LDAP authentication (which I would assume the majority are not using), correct casing based on the user-config file shouldn't have undesirable effects: if you can log in with what's in the user config file then correctly saving the cookie file with that username shouldn't negatively impact anything. On the other hand if you do not save the cookie file with the same user name that is in the user-config file, but you continue to use the user-config file to generate the localPA variable, then you may have problems on case sensitive platforms.
If this fix seems to difficult (I don't believe it to be) or you're suspicious of the logic, you may want to place a warning in the setup instructions. I've added a comment on the wiki for userconfig.py that people using *nix systems should be aware that by default mediawiki has uppercase user names.