A lot of the discussion on this post ended up being about LessWrong norms. I've moved that particular thread over to the comments here, and left a comment there pointing over here.
(Some of those comments, including the initial one, were object-level relevant to this post. I apologize for moving all of them indiscriminately. Our comment-moving-features are a bit janky and it's easier to move an entire thread than individual subthreads. I also apologize for breaking a lot of the comment-permalinks in that thread, and we'll look into fixing those. Meanwhile, you can actually still hover-over the comments in question on LW to see a preview of the comment, and you can also copy the comment-hash from the link and apply it to the new post to get a working link)
This may not be Said's view, but it seems to me that this obligation comes from the sheer brute fact that if no satisfactory response is provided, readers will (as seems epistemically and instrumentally correct) conclude that there is no satisfactory response and judge the post accordingly. (Edit: And also, entirely separately, the fact that if these questions aren't answered the post author will have failed to communicate, rather defeating the point of making a public post.)
Obviously readers will conclude this more strongly if there's a back-and-forth in which the question is not directly answered, and less strongly if the author doesn't respond to any comments at all (which suggests they're just busy). (And readers will not conclude this at all if the question seems irrelevant or otherwise not to need a response.)
That is to say, the respect of readers on this site is not automatically deserved, and cannot be taken by force. Replying to pertinent questions asking for clarification with a satisfactory response that fills a hole in the post's logic is part of how one earns such respect; it is instrumentally obligatory.
On this view, preventing people from asking questions can do nothing but mislead readers by preventing them from noticing whatever unclearness / ambiguity etc the question would have asked about. It doesn't release authors from this obligation, but just means we have to downgrade our trust in all posts on the site since this obligation cannot be met.