Ever used Lotus Notes?
And now the expand/collapse UI pattern with right/down arrows or triangles is standard (e.g. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/de...). Don't get me wrong, the example button is terrible UI, but an interesting example of how norms change.
On more than one occasion I have misinterpreted the upvote icon on HN to be "collapse thread".
To this day, I still am unsure if they were joking.
A day never goes by without a delight.
Edit: IBM Notes