We have too many pages that use CSS style everywhere. This complicates their editing a lot.
Why couldn't we have support for a <style>...</style>
element that would be scoped to the editable #content ?
This would apply to lots of data tabes that or now require too much complex editing in each cell.
Of course the same restrictions about the CSS supported would apply: no Javascript for example. But everything we can already insert in a style="" attribute should be possible to restyle elements via CSS selectors, automatically scoped within #content.
Topic on Talk:Requests for comment/Scoping site CSS
You can be interested by the sister RFC Requests for comment/Allow styling in templates.