JS or user submitting a form -- some form of client interaction.

You can do requests to the site using pure CSS as well, using something like `.site:visited { background-image: url(/logging/site); }`

those kind of tricks are already blocked by browsers, as the article explains

This one does not really need JS, the captcha could be done with an HTML form and checkboxes.

captchas which are not working with noscript/basic (x)html browsers are definitive no-no anyway.