I'm wondering if this might be a bug.
Trying to tag a user in the comments section and see if he gets notified. @username works fine in the comments section, I can see a suggestion for him. But he does'nt get at notification.
In tblNotificationMessage Sender is "AD\username" and Recipient is only "AD". So I think this is the bug. That recipeint has been chopped on '\' and only takes the first part of the whole name.
I tried out the same scenario in alloy tech. I created two users in the group "WebAdmins", one with the name "testaccount" and another with "TEST\person". I could recive a notification to "testaccount", but not "TEST\person".
Best regards, Christoffer