Some styles are implemented as UA rules instead of presentational hints #13111

What is the issue with the HTML Standard?

https://html.spec.whatwg.org/multipage/rendering.html has lots of styles which are "expected to apply, as presentational hints".

For example, from https://html.spec.whatwg.org/multipage/rendering.html#tables-2

table[border] > tr > td, table[border] > tr > th,
table[border] > thead > tr > td, table[border] > thead > tr > th,
table[border] > tbody > tr > td, table[border] > tbody > tr > th,
table[border] > tfoot > tr > td, table[border] > tfoot > tr > th {
  /* only if border is not equivalent to zero */
  border-width: 1px;
  border-style: inset;
}

No browser implements this as a presentational hint, they do it using the UA origin. The difference is observable:

<!DOCTYPE html>
<table border="50">
  <tr>
    <td style="border-style: revert"></td>
  </tr>
</table>

You can still see border-style: inset in Firefox, Chrome and Safari, because it's in the UA origin. If it was a presentational hint, it would have been reverted, according to https://drafts.csswg.org/css-cascade-5/#preshint

This other example is an actual presentational hint: https://html.spec.whatwg.org/multipage/rendering.html#flow-content-3

pre[wrap] { white-space: pre-wrap; }

as observed in this testcase, which outputs pre, because white-space: pre-wrap gets reverted since it's an actual presentational hint.

<!DOCTYPE html>
<pre id="target" wrap style="white-space: revert"></pre>
<script>
document.write(getComputedStyle(target).whiteSpace);
</script>

I think all the styles need to be reviewed one by one, check what browsers do, and update the spec accordingly