The method by which the favourite gets into the list is not discoverable. Why would anyone think that clicking on the time a submission was made would be the route to adding a favourite?
And the list of favourites would be much more discoverable if it were simply a link next to your name on the page. After all there is plenty of space at the top right of every page on HN
"There's no free will," says the philosopher; "To hang is most unjust."
"There is no free will," assents the officer; "We hang because we must."