Link cards fill in the blanks
Post a link and a placeholder card appears at once, then turns into the real preview while the page behind it is still being read. You never hit reload.
You paste a link, hit post, and the card slot is already waiting. It is a shimmering grey rectangle in the shape of a link card. A couple of seconds later the site name, the headline and the description drop into it, and you are looking at the finished card without leaving the page you posted from.
Credit goes to xHeaven, who taught the card to wait for its own page. A fresh link counts as pending until the background fetch fills it in, and the card asks for it again after 1, 2, 3, 5, 8 and 13 seconds. That makes six tries over about 32 seconds, and it stops the moment it gets an answer, hits an error, or you navigate away. It works in feeds, on profiles and under replies, and playable links such as YouTube skip the wait entirely.
One catch is the clock. If the page takes longer than those 32 seconds, the grey card disappears and you are back to an empty slot until you reload. That bites more often than you would like, since a failed fetch backs off 60 seconds and then 600 before trying again.