StackExchange recently implemented a feature that allows users to "follow" a post in the sense that they get notified on every edit/comment below that post, as if they were the post owners.
I find this to be very helpful, especially on meta, where one might want to follow discussions on answers, even if they are not actively mentioned in the comment.
But now I have a different problem. When I am pinged directly below a post that I follow, I get notified twice. This is definitely a bug, since it is not the case when someone pings me in a comment below one of my posts.