Greetings. Previously you mentioned [] you were working on something to allow non-ucfirst usernames. It seems to me that users/User.php simply disallows this, but without any explicity need for it. I would propose a simple patch to User.php to not do ucFirst (two functions) if wgCapitalLinks is false and that the USER namespace is not explicitly whitelisted as an exclusion. But are there hidden internal dependencies in mediawiki on a cap-first username? What about well-known extensions? (For instance, PluggableSSO/PluggableSSOAuth:getcanonicalName())
Topic on User talk:MarkAHershberger
I have a patch in gerrit for this. I lost interest after a while, but maybe it would be a point of reference for you.