I'd like web browsers to allow user-controlled privacy deviation where a website in a sidebar is allowed to know the URL in the main pane. The sidebar website c

I'd like web browsers to allow user-controlled privacy deviation where a website in a sidebar is allowed to know the URL in the main pane. The sidebar website can run a group chat, run their own spam and comment moderation, and allow for discussion on the main window. I'm sure it's ripe for abuse, but my base case is a less biased place for people to talk about what's on a website on the main pane. Friends, companies, any tribal alliance can run their own service for the sidebar in a standard way to keep it easy to swap around. Basically it's a way to steal the comment section from websites.