So I SSHed in. I got the message. Then I saw all the people freaking out here and couldn't believe my eyes.
Ask yourself this:
How often do you SSH in to arbitrary hosts? Ones that you don't control, or work for, or trust with your source code?
Did you really expect that you could give the same long unique base64 string to a bunch of different hosts and NOT have them connect your identity between them?
Do you not understand that the whole point of public keys is to uniquely and reliably identify yourself to an arbitrarily large number of parties?
Honestly, the only real eye-opener here is that Github gives out your public keys and can be scraped to collect all of them. But some of us have been using that functionality to share / snag each other's public keys for a long time now anyway.