In Charcoal HQ, from time to time, we create a detection for a username which has been used in a lot of spam posts across the network. We need to make sure that the username being considered for use in a detection won't catch posts by genuine users, so we search for the specific username to see if it is used by legitimate users.
Usually, we conduct this search on Stack Overflow and the sites where the user has left spam posts, but this is not as thorough a search as we'd like, as there are many other Stack Exchange sites.
Is there any way to search for users with a specific username across the network, even if they don’t have any posts?