There is an API of sorts that pings your blog if it gets published to eg; Hacker News but I can't remember the name currently. It's opt in and I think Lobsters

There is an API of sorts that pings your blog if it gets published to eg; Hacker News but I can't remember the name currently. It's opt in and I think Lobsters uses it? Anyway, it's not exactly what you're after as it wouldn't ping you about individual comments, just threads in general