> He changed his profile picture to a photo of himself so it was much easier to see which Jason Signal contact corresponded to that Jason.
This still leaves the risk of people deliberately changing their username+profile picture to match that of Jason to trick you to invite the wrong Jason to the group chat
In #Conversations_im we try to show the Jabber ID (not just the username) in relevant places (during invites, for new chats)
For #Signal that would be the phone number, I guess