For usenet and mailing lists, this is handled on the client side by read/unread tags on messages. Web forums haven't yet found a way to do as good a job imo, le

For usenet and mailing lists, this is handled on the client side by read/unread tags on messages. Web forums haven't yet found a way to do as good a job imo, leading to a lot more reload-and-scan type activity that feels even more twitchy than the old kind of check-for-new-messages twitchiness. Reddit does notify you when there's an unread direct reply to one of your comments, which is a replication of one part of that functionality.