User interaction may overwrite CSS

[iherman]

Fix #1605

The only change is using the sentence in #1605 (comment)

[mattgarrish]

I agree with the initial lack of clarity about what this bullet is requiring of reading systems, but we're losing the
recommendation that reading systems provide user control over styling in the rewrite. From an accessibility perspective, that's a very important thing to have.

But maybe if we have to write an (informative) accessibility section in this document per #1608 it can go there.

I'll take a skim through the html spec and see if they touch on this at all.

[dlazin]

Thanks!

[mattgarrish]

I couldn't find anything in the HTML or CSS specs. Only UAAG goes into this a bit, but even it's pretty vague. Short of mandating the control a user has to have, the language we had was about as good as you can get.

I'm going to take this up when I get to the accessibility section instead.