Thank you for your efforts and for letting me know. I updated to 1.9.10, and unfortunately both bugs are still present in a fresh vault.
I tested on the same personal document that prompted me to make this bug report. The scrollbar still moves with each character press, although not on every line. Sometimes it looks like it’s moving, sometimes it works as it should, other times it looks like it’s resizing constantly. You can see all 3 behaviors in this 30s clip of me typing: https://imgur.com/SXcjAlq
However what I can say is that the example text in my original post does not exhibit this bug anymore.
I created another obfuscated document which does still cause this bug so you can reproduce it on 1.9.10: https://pastebin.com/Tzii8VNc. Please see this screen recording of me reproducing it using this exact same pastebin. The bug depends on scroll position, so you’ll need to do exactly as I did to reproduce it.
Lastly, the other bug you linked to on Jul 6 has not been completely fixed, the Outline view still moves every ~2 seconds while typing. That thread was locked, so I’m sending the video of the bug here on 1.9.10: https://i.imgur.com/DKqQQaL.mp4