This is really great. I think we're going to use this for helping us highlight parts of the YC application that sticks out to the partners. Very interesting to see that what you actually store in local storage.

[{"startOffset":35,"endOffset":42,"startContainerPath":"html>body>div:nth-of-type(1)>div>p:nth-of-type(1);0","endContainerPath":"html>body>div:nth-of-type(1)>div>p:nth-of-type(1);0"},{"startOffset":32,"endOffset":7,"startContainerPath":"html>body>div:nth-of-type(1)>div>p:nth-of-type(1);10","endContainerPath":"html>body>div:nth-of-type(1)>div>p:nth-of-type(1)>code:nth-of-type(3);0"}]

One thing I think we might tweak for ourselves is to also store a copy of the string in there.

Thank you so much for sharing! I bet people would love an example showing how to use this to sync highlighted examples across user accounts. Hopefully, someone will do a Show HN of that!