I want to know who earned the highest reputation in a single day.
Here this user earned 727 reputation in a single day. How can I find another user who has more than this on Stack Overflow?
That belongs to David Robinson, who earned 1550 reputation thanks to three bounties worth 500 reputation and five answer upvotes on July 6, 2013. The full post and the queue to find that out is in this link: https://meta.stackoverflow.com/a/267558/4052384
And no, Jon Skeet does not have the record unfortunately.