They do not; if you sort as unsigned ints then negative floats sort above positive ones, and if you sort as signed ints then the negative range is reversed. IEEE floats are sign-magnitude, not twos-complement.
The interface also allow to comment, post and interact with the original HN platform. Credentials are stored locally and are never sent to any server, you can check the source code here: https://github.com/GabrielePicco/hacker-news-rich.