“The annotations I have seen are often more snark than substance,”
Same experience, even in the Genius guidelines. The tool’s affordances (and name) revolve around snark. In the abstract, there’s nothing wrong with that. We need spaces for people to have fun, even if it’s at the expense of others. But the startup is based on a very specific idea of what constitutes useful commentary. That idea is closer to pedantry, snark, intellectual bullying, and animated gifs than on respectful exchange.