I agree, sort of. I think there should be a natural flow from highlights to long form clients.

Every kind 1 client should also render highlights in the main feed, ideally. If the client also supports displaying long-form notes, I think those should have their own feed and tapping/clicking the highlight should take the user to that feed. If the client does not support displaying long-form notes itself, it should open a web-client like Highlighter.com when the user taps/clicks on the highlight.