Is it poor etiquette? As delineated by Quora’s purpose for the site, no, because they built that feature in, and because the site keeps insisting that it is a Q&A and not a discussion site.
What do I think? What Ben Sinclair said. It’s people’s right to, but I don’t have to like it, and I don’t. Especially the dismissive “if I wanted a discussion, I’d have gone to Reddit” response that I’ve seen from writers like Ernest W. Adams. He’s a great writer, but if he’s not interested in a two-way exchange on any of his answers—well, I’ve increasingly lost interest in engaging with him one-way. Yes, it’s his right to block comments, and yes, Quora is happy for him to. And it’s my right to view it poorly, and “go hang out on Reddit then” is not a meaningful response to that.