Remove Gravatar integration
tl;dr: In multiple ways, Gravatar is bad for privacy for people who use services that use Gravatar (even when they're not aware Gravatar exists). Please remove it.
MD5 hashing an email address is not good enough to hide it. In gitlab-ce#43521 an effort is being made to hide email addresses for web-based operations, so my request here fits with that spirit.
Gravatar tracks you for commercial reasons without a way to stop it. I believe it would be unlawful to track email addresses of even non-users, but I wouldn't put it past them.
You could argue that "if you care about this just set an avatar", but most people are not aware of this insanely big flaw and have no incentive to do it. In the end, it's up to the service provider to not expose users' data by default without consent. Also, the whole Gravatar service should just die.
For these reasons I would recommend dropping Gravatar support altogether. Thank you for your consideration.
End note: Some sort of default avatar is of course nice to have. There are geometric pattern generators or things like the Cat Avatar generator.