Earlier quoted context omitted.
If I reply to a post or comment that's over several days old there's almost no chance the author will ever see it. That is a Good Thing.
No, it's not If you ask a question, and I happen to see it a couple days later and can answer it, why would you not want to see said answer?
Especially considering somebody who's particularly motivated to find delayed answers to specific questions can always bookmark the particular comment and check it manually, or just occasionally scroll-back through the "threads" page or whatever. If they're not motivated enough to do that, then maybe the discussion wasn't that important to begin with.