To simplify writing, I'll simply refer "users with same profile display name (case insensitive) user" as "users" (with quotes), and an arbitrarily user picked from "users" as "user" (with quotes).
Suppose that multiple "users" participate in the same chat room and/or comment thread. How can one effectively ping a specific "user"?
From the accepted answer in How do comment @replies work?, matching of "user" from "users" is done by reverse chronological order. It suggests typing out full names without spaces to differentiate. However, that doesn't work for "users". There's no way to Avoid pinging multiple users in chat.