alt Hacker NewsHN does not record your key strokes until and unless you click the reply link…and then only if recording your final edited comment counts as recording your keystrokes.
On the other hand, your browser might be recording each of your keystrokes just because it can and if your browser does, those keystrokes are not going to HN.
It's trivial for HN to record your keystrokes. Any application that can read your keys can record your keystrokes - its fundamental to how software works. You wouldn't be able to write a game if you couldn't.
The distinction you are trying to make a is a distinction without a difference. If you don't want sites to "record your keystrokes", then don't use a computer. Trying to paint this as nefarious is a losing battle and completely undermines any awareness you are trying to bring about.