Thanks guys for the reply. Hmm, I was thinking of a more common situation where the user goes to bed or whatever, and comes back after 8 hours. In that lapse of time, there can easily be 50 replies to a hot topic, which means 50 notifications. This really irritated the users of my non-Discourse forum, and they pretty much nagged me to death until I hacked together a system to make it only send one notification until they return. I think it’s a critically important option for Discourse as well, at least for some communities.