Realtime comment notifications currently open a connection called event.js, which closes after 30 seconds. Afterwards, a new one is opened, which we use to push information like new comments, replies, and when someone is typing a reply comment to the embed.
Because of how this works, it will often fool performance tests into thinking it's taking too long to load your site. In reality there's no perceivable loading or performance impact for site visitors, nor will your search engine ranking be affected by this.
Realtime services are completely independent and asynchronous and are triggered only after the embed is fully loaded.