It looks like his thumbnail gravatar icon is just messed up.
https://i.sstatic.net/WvfsF.jpg?s=48&g=1
However, the small/medium/large alternatives look fine:
https://i.sstatic.net/WvfsFs.jpg?s=48&g=1
https://i.sstatic.net/WvfsFm.jpg?s=48&g=1
https://i.sstatic.net/WvfsFl.jpg?s=48&g=1
Probably just needs to update the picture again.