We don't need the .rtl prefix for some rules that should be overridden by responsive.css. On the other hand, some rules from bidi.css should override rules from responsive.css so they should keep the .rtl class.

For example, in the attached picture the forum title (#site-description) should get 'float: none', but bidi.css overrides with 'float: right' because of its specificity.

We will create a pull request with the fix soon.