This depends heavily on the website in question and how well the comments are moderated/curated. The Online Photographer [0] is my goto example of a blog where the comments are excellent (and a key part of the value gained from visiting the site). The trick in this case: every comment goes through a moderation queue before it's posted. Some then get featured as part of the article.

[0]: https://theonlinephotographer.typepad.com/the_online_photogr...