I don't understand the need for expensive animations or the imagined use case of opening/closing the comments sidebar a hundred times while reading the paper. Why does opening one note hide all indicators of other notes? (It seems if you're reading at above ~1500px browser width, it shows them as small dots, but removes the preview text of the note). I should just be able to leave it open and have new notes/comments appear as I scroll past the relevant section.

Why does clicking anywhere on the document, or highlighting any text open up a "write a new comment" sidebar? Do they really think there are going to be more users writing comments on a paper than there will be copy-pasting a few sentences from it?

It feels like the primary purpose of the site is for users who want to comment on papers, and not users who just want to read papers. For the latter group, it's a really poor experience.