As a developer I have to request revisions from the designer and the actual client. It would be amazing for the staging url to be able to turn on comments so all I have to do is send the staged website over to everyone involved via the staging links and they can see/comment and requested edits live.
It would be link integrating markup into our staging urls.
Then it would make it to where we don't have to add them to our accounts, no one has to sign in to comment, nor do you miss any animations or embeds that are only visible on the live domains.