Follow without losing your place in the log
Click Follow on a developer and the button, your counts, and the live sidebar change in place. Trending keeps its exact ranking and the posts in front of you stay put.
You are twenty posts deep in Following, cursor parked on a commit you mean to read, and you click Follow on the developer beside it. No progress bar sweeps the top of the page, no jump to the start, no flicker of the whole feed. The button changes, your follower count moves, and the new commits slide in above you while that commit stays under your cursor.
Credit goes to xHeaven, who taught the follow button to ask for less. A follow now returns only your account, the live-following sidebar, and, on Following, the posts and the empty-state suggestions. Latest and Trending keep their loaded posts and their ranking untouched. On Following, the request carries the id of the oldest post you have loaded, and the server sends back everything newer than that post, plus one more page of 20, so the cursor and the scroll anchor survive. Follow writes and page reads queue up and run one at a time, so a quick second follow lands after the first.
One catch. There is no ceiling on how much comes back. Scroll a few hundred posts into Following, follow someone, and that single response hauls every one of those rows over the wire. Deep in the log, the follow is cheap on the eyes but not on the network.