I was looking at a puzzle on the Puzzling riddle sandbox, and I clicked on the user. This what I clicked on:
That brought me here:
Note the rep difference.
Then I clicked in 'Main user', and I got a page not found:
So I went back to the Meta profile, and clicked on the Puzzling thingy on the accounts, and got this:
(Sorry, don't know what happened with my screenshot.)
It can't be the name difference in the URL, because SE accounts for that, last I saw. So what's happening here?