Us self-hosted folk have been control where widgets are displayed for a long time with plugins, but when you’re on WordPress.com, you just don’t get the same features — which should be expected, primarily for security and scalability reasons.
One big piece of functionality has been the ability to hide and show a specific widget when viewing a specific type of content.
In a recent announcement by Christopher Finke, a design engineer at Automattic, he writes about how to use the new Visibility function for widgets.
I use Widget Context here on WP Force, which I find easier to use. The new Visibility function feels a bit clunky, even though I’m sure that it’s more scalable in the backend. Everything on WordPress.com has to be really efficient because of how many sites that WordPress.com runs.