Usernames vs. Nicknames

I would like to suggest that it is not a good idea to be publicly using the username as part of the URI for the ActivityPub plugin. Using the username is creating a potential vulnerability on sites that wish to use this plugin. In Wordpress usernames are the login ID's for user accounts. This means that the URI is exposing the user ID of accounts publicly.

Instead it would be better to use Nickname, and handle the lookup to map them to the Username. This way the account login ID is kept within the system and not made public.