@MartinR Regarding hidden communities, you can find more information on Meta Stack Exchange, there is even a separate tag for this.

For example: How do I hide my accounts on a specific Stack Exchange site? and Hidden profiles are not hidden at all.

> Profiles on a user's Hidden Communities now hide the link to the network profile for everyone but the user and site moderators. Moderators on other sites will not see the link, but should be able to verify a connection to a user on their own site by following the link to the network profile.

This came up recently also on MO in connection with this question: Flood of Similar New User(s). chat.stackexchange.com/transcript/message/50653124#50653124

My last answer happens to be a community wiki answer for some reason - can someone undo that?

@ThorWittich Next time, please raise a flag.