We could consider adding a guideline asking people not to post such things. The problem is that sometimes such comments are helpful for the owner of a site, who either shared their own work or happened to be on here when someone else did.
My guess is that's pretty unusual, and that if you looked at a sample of, like, 20 of them, in at least 19 cases whatever was being complained about would remain the case on the website in question, indicating that the site owner did not get value from them. Meanwhile: those comments really are a pox on the threads; it'd be better if users were in the habit of downvoting them to keep the top of the thread clear, which a guideline would accomplish.
Discuss substance, not presentation, unless presentation is the topic of the story. Comments about web design and readability are off-topic. Advice for authors is best delivered through a polite private email.
Devil's advocating here, because I agree more with your sentiment:
That comment has sparked a larger subthread specifically about Twitter as a medium, rather than the content of the post. This specific subthread is so popular, it's near the top of the page every time I refresh this post. So we could say it stifles discussion, also because people are prone to voting up a comment like that despite the fact that it's not really relevant to the post.
90% of links, have some kind of: "doesn't work on my mobile... format sucks, i don't like the colors, etc... etc.." comment.
It is pure infantile/juvenile bikesheding and distracting from the point of the conversation/link that has nothing to do with formatting.