Thanks for the response, Robin, but maybe there's a bug in it. I'm not sure if anyone has tagged me with an @ symbol before now, but someone just quoted my text and then tagged me with an @ (perhaps for the first time). When I go to the quotes and mentions tab, it doesn't show me being tagged. It just shows that my text was quoted.
As for the notifications, it would be great if you could choose what types of notifications you want to receive by email. For instance, I would not want an email every time someone quotes my text. That happens too often, and I find out about it already by looking at my topics tab and seeing what is new in the threads I've participated in. I would like to know, however, if there is a thread in which I am not participating but someone tags me with an @ in it. I might be drawn to that thread. If I got an email, I would notice it. If I had to go to a notifications tab, I don't think I would do that regularly. Similarly, I would like to get someone's attention by tagging them in a thread with an @ even if they were not participating. If they got an email, it would be more likely to get their attention.
I hope that makes sense. It seems like you may be contemplating this with the link that allows you to configure notifications.
Anyway, great site! Just a few suggestions.