Why are the usernames case sensitive? michaelapproved is not a valid username when searching but MichaelApproved is. Does HN allow for different case usernames or is it something that was overlooked during development of the search feature?
HN overall has case-sensitive usernames. Drove me batty until I figured it out. You can ask pg why he went with that particular design choice.
The code can be downloaded from http://ycombinator.com/arc/arc3.tar Note the code is from 2009 and didn't exactly match the running HN code at the time, so any conclusions from the published code aren't guaranteed. I did an analysis of the HN ranking formula back in 2009 - http://www.righto.com/2009/06/how-does-newsyc-ranking-work.h... - but the live formula is surely very different from the published code by now. And ironically, that article got about 0 upvotes so it didn't rank well :-)