What is the maximum number of @somenamehere that I can use in a single chat message to ping people? Asking out of curiosity rather than any practical standpoint as I can't envision needing more than a few.
What is the maximum number of users that you can ping?
In all seriousness, there doesn't seem to be one, at least for me. The only real limitation is your patience and your typing speed. And the amount of flesh left on your fingers after you've typed that many keystrokes.
On a side note, please don't support the fool that invented @@@@ and @## though. They used to work, and by now probably have a replacement (unforuanately). Ping grenadiers are not amusing.