Vulcan/packages/nova-subscribe/lib/callbacks.js

import Telescope from 'meteor/nova:lib';
import Posts from "meteor/nova:posts";
import Users from 'meteor/nova:users';

// Notify users subscribed to the thread

function SubscribedCommentsNotifications (comment) {
  if (typeof Telescope.notifications !== "undefined") {
    // note: dummy content has disableNotifications set to true
    if(Meteor.isServer && !comment.disableNotifications){

      const post = Posts.findOne(comment.postId);

      let userIdsNotified = [],
          notificationData = {
            comment: _.pick(comment, '_id', 'userId', 'author', 'htmlBody', 'postId'),
            post: _.pick(post, '_id', 'userId', 'title', 'url')
          };

      if (!!post.subscribers) {
        // remove userIds of users that have already been notified
        // and of comment author (they could be replying in a thread they're subscribed to)
        let subscriberIdsToNotify = _.difference(post.subscribers, userIdsNotified, [comment.userId]);
        Telescope.notifications.create(subscriberIdsToNotify, 'newCommentSubscribed', notificationData);

        userIdsNotified = userIdsNotified.concat(subscriberIdsToNotify);
      }

    }
  }
}

Telescope.callbacks.add("comments.new.async", SubscribedCommentsNotifications);