Okay I know the title is pretty vague but I didn't know how to articulate it.
Basically, I want a plugin that sends email notifications to users who opted-in only if they specifically got replied to.
WordPress has its built-in functionality for comment threading/replying, so instead of bombarding the user with emails each time a new comment is posted on a post they've subscribed to, I'd like to give them the option to only be notified when they specifically get replied to.
I can develop this myself if need be, in fact, a preliminary search yielding no results seems to point at this.
My question is, what hooks would I take a look at? Looking at other notifier plugins, I see they make use of
comment_post and others which I can come up with myself. More specifically, how would I go about knowing if user x got a direct reply?
I understand how the subscription system and all of that would work, my only concern is how to tell if a subscribed user received a direct reply through the built-in commenting system.