If you upvote or downvote a post on Hackernews, and it failed (e.g. because you have hit the 1-request-per-second limit), there is no error, and the vote silently fails.
Only if you refresh the page will you see that your vote actually didn't go through.
It’s always been this way.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/204