Plenty of times I've received replies to comments that were themselves replies to posts that were a fair number of days old.
It depends on how often that person visits HN, how busy is their "threads" timeline and how deeply they go into it. Then, finally, whether or not your comment requires or provokes a response.
It can happen, but after a few hours it’s _extremely_ rare for people to read comments. If you’re an infrequent commentator, you’ll notice this. You’re almost never going to see your points change if you haven’t made a comment that day. On the rare occasion it does happen, it’s going to be one point for a post made in the past week.
Your reply actually made me curious and I logged into an old Hacker News account that I hadn’t used in a few years. Hundreds of comments on that account, many that had a very positive responses (thousands of total points). Yet not a single point was given since I switched accounts, likely because close to no one has read any of those comments since they were made.
On web forums it’s not unusual for me to get replies and reactions for comments that were made a decade ago.
It depends on how often that person visits HN, how busy is their "threads" timeline and how deeply they go into it. Then, finally, whether or not your comment requires or provokes a response.