> Slack & notion make me close my eyes while typing, just because the delay between key press and pixels lighting up is so long that I get confused. It's like speaking with a 400ms or so echo of yourself being played back. Hugely distracting.

That reminds me of this blogpost [1]. It's definitely possible to optimize the input latency of rich text editors in the browser: they just have to be close to the metal of the 'contenteditable' browser api.

[1] https://juretriglav.si/what-happens-when-you-type-a-single-l...