Handles go case-blind
Paste a profile link in the wrong capitals and it opens anyway, then slides over to the spelling GitHub uses. Profiles, people lists, commits, photos and organizations all play along.
You paste a friend's profile link out of a chat window, all lowercase, and hit return. The page opens, and the address bar quietly rewrites itself to @OctoCat, with your ?tab=replies still hanging off the end.
Credit goes to mnapoli, who taught the @handle pages to stop caring about capitals. Every lookup compares lowercased handles against a lowercase index the profiles table already keeps, so a link in any case finds its person. When the capitals don't match, the page answers with a 301 and sends you to the handle's own spelling, query string intact, repeated keys and all. It covers profiles, the following, followers and mutuals lists, commits, commit photos and organization pages.
One catch. The detour only fires for commits you can already see. A pending commit reached through the wrong capitals answers 404 instead of pointing you at the right page, so only its author gets the corrected link. Everyone else sees the same dead end as a commit that never existed.