I have often wondered why this facility was withdrawn.
It was handy on occasion (I think I used it about twice in ten years) and seemed to be rarely abused, and only then by those who weren't aware of the convention (that you only used it after being invited to)
I think it just hasn't been fixed to work yet. If you look on the main Helproom (not one of the threads) at the bottom just above the dark grey area there is a key to symbols 'What do the Forum icons mean?' and one with grey envelope and head &shoulder silhouette is listed as 'Email Forum user'