If you search the archives, you can see plenty of people asking this and a few third-party sites that will notify you of comments.
Last year, dang posted this:
> I look at it this way: it's designed for engaged, prolonged discussion if and only if people continue to be interested enough in it to remember. If they aren't, activation energy falls below a certain threshold and attention naturally moves on to something else. That seems healthy for curious conversation, which fits the prime directive of HN (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...).
> What we don't do is resort to technical tricks to keep that energy buzzed up. We're optimizing for curiosity, not engagement.
You can use http://www.hnreplies.com/ for email or https://hnrss.org/replies?id=coreyhn for RSS.
It won't notify you of your upvotes however, which is what most people are after. Only manually refreshing "news.ycombinator.com/threads?id=you" opens that narcissism drip.