here's an example:

    https://developer.twitter.com/en/docs/tweets/curate-a-collection/api-reference/get-collections-entries

scroll to the very end of the page, where twitter cheerfully asks "Was this document helpful?"

why did they choose a happy/sad face, instead of, I don't know, regular buttons?

who's the indented audience of that page? kids? I think not. It's probably a 30-something year old grumpy, bearded guy, yet...