bbPress.org

1. That is oembed cache you are removing with WP-Sweep, not the oembeds itself.

5. That was just 8-9 months ago. Some plugins do not need to update as frequently as others. This plugin basically is just using some bbPress hooks and filters to create its functionality for itself.

12. What browser are you using? I could test this in a minute. And I guess any theme that is based off of the HTML5 boilerplate like HTML Blank theme, I would come across the same issue as you??