My biggest pet-peeve with GH code review is that line-comments are automatically folded whenever that line of code is changed. So if the changes to that line didn't relate to your CR or if they didn't actually fix anything, then your comment will pretty much be lost to time.
Plus, it would be nice to see the discussion around a particular line without having to go through the entire PR and unfolding each conversation to see if it's the right one.
Then give Reviewable (https://reviewable.io) a try. :) Comments remain open until acknowledged / resolved and are automatically displayed at the nearest applicable line in every diff.
Plus, it would be nice to see the discussion around a particular line without having to go through the entire PR and unfolding each conversation to see if it's the right one.