This is cool. I wish this sort of analysis existed for many major websites! The reason I think this would be useful is the accessibility of the results - we'd be able to consider the various analytics within the context of something highly familiar (the mention of Slack still using "text/..." is one such example).

Although... hmm, maybe I don't want all websites scored. Arc (ie, HN) would probably rank 0.5/10 in terms of technical design (I begrudgingly admit the Spartan UI could be worse). Upvoting is done by creating an empty image then loading it - but the "hide" link uses XHR, so that's a bit inconsistent; the layout is based on tables... and still uses the old 1x1px spacer image trick for padding!!1; there's absolutely no ARIA to be found anywhere, so I wonder what screen-readers think of it (a valid consideration, I've read comments by blind users here); and the Firebase API is read-only and doesn't permit posting/interaction, so if I want to make a 3rd-party app, I'd have to ask users for their passwords. That works for app storage but localStorage is neither encrypted or "reasonably resilient", so that won't work in a Web framework demo context. I have a lot of reluctance to give out my HN password in a world of OAuth2, all the more when I consider that HN is regarded more highly than other communities such as reddit, twitter, etc. I think this could explain why most 3rd-party HN demo apps don't allow posting, and it's sad.

Incentive to make own, better website intensifies

And I'll make a note of this person, and ask them what they think of it when it's live.