There are still the same error messages with this plugin. Its last update was in 2011.
I give me some days to write our own plugin. It would really be important to have such a feature! In principle, I know how to do, creating events for the event log if a user is pinged and let these evaluate by a small change in the history plugin. The user would then get the well known yellow dot at his username, when he logs in.
However, there is an issue that I do not yet know how to solve. Let us assume that we have two user, "Peter" and "Peter Blackhole". In a post there could be pings like
@Peter Can you explain ...
@Peter Blackhole As you explained ...
It would be very difficult to distinguish between the two pings. Could you eventually live with the directive to put a colon after the full name? Examples:
@Peter: Can you explain ...
@Peter Blackhole: As you explained ...