Keybase GUI Version: 2.7.3-20181005191950+83f5d808a7
OSX 10.14 Mojave
When I hit Cmd+Shift+f, a common IntelliJ IDE family shortcut for "find in x", my keybase public key fingerprint is pasted into an input that has focus. (Verified this occurs in PHPStorm, TextEdit, and iTerm. FireFox and Chrome don't seem to be affected. Not sure why some programs have this issue and others do not.)
I have this issue. Not only does it paste my key into the input, but also intermittently triggers the passphrase prompt.
This appears to be an issue with OpenPGP registering keyboard services in OSX.

So likely not a bug with Keybase. Disabling this service fixed the problem.
System Preferences -> Keyboard -> Shortcuts -> Services
Most helpful comment
This appears to be an issue with OpenPGP registering keyboard services in OSX.
So likely not a bug with Keybase. Disabling this service fixed the problem.
System Preferences -> Keyboard -> Shortcuts -> Services