[hnand]

That's an interesting UX problem. Have you tried Anchors ("#" buttons)? Do you feel like it would be convenient if there was an option to mark all new posts as anchors? You could jump between them with "previous/next" buttons.

[germinalphrase]

Highlight “new comments since last thread visit” without altering thread structure?

[hnand]

Thread structure won't be altered, new comments will be marked like here https://github.com/devandsev/HackerNews-Support/wiki/Guide#a... and you'll be able to iterate over them.

Direct link to the video https://user-images.githubusercontent.com/17564071/236939878...