If ChatGPT is given an entire message (sub)thread as input, it will decide which parts, if any, it responds to. Sure, that's a bit different from how humans tend to read and reply to these threads.
If you mean feeding it the messages one at a time, then, sure, it will respond to each of them because that's what its default "goal function" is. (I assume that we're talking about a single "conversation" here so the context is retained – feeding it each comment out-of-context would be very unfair.)
If you prompt it to only reply to messages it considers "interesting" in some way, and return "I'll skip this" for the others, it would certainly do that.
The original question was, given that there were X comments which could be replied to on this page, how and why did the poster decide to respond to the one to which they responded, rather than either "all" (like ChatGPT would) or "none?"