Hi,
this is not a bug, username is the only unique and human readable user info, so it is used for build SEF url. Google indexes only public links and you have some public user link on your site (
i.e. author link from
https://www.ghostlyhaks.com/blog/apple-efi/23-efi-deobfuscate ).
How to remove from Google indexes results?
I don't know, Google have a cache system so it be take many time. Anyway to remove future indexing you need to edit your robot.txt in the root of site (
https://en.wikipedia.org/wiki/Robots_exclusion_standard )
How to remove author link from article for guest users?
if this link become from our author plugin then you can simply set this plugin with Registered ACL. With this it will be disabled for guest users.