I never found a solution to what I actually want/need:

- Snippet bookmarking. I don't want to browse to the whole page again, just highlight and save the piece of it I need to bookmark.

- Annotations. I want to highlight, underline, bold, and comment on what I've bookmarked so that I know why I bookmarked it or what I intended to remember later.

- In an open standard, like JSON, so that I can do things with the bookmarks other than view them in your proprietary website.

Seems like a fairly simple ask, but all the software that promises to do it fell short of my expectations.