thank you for working on this.

aside from the comments i left in my quick review, does it make sense to explicitly call out as a note that aria-level is not considered/taken into account with these attributes?

from re-reading the issue this stems from, i'm assuming people are likely thinking that if someone declares an aria-level on a heading, the value of that attribute is what the heading level will be exposed as, yes?

Or to be very clear, do people agree with the following:

<div headingoffset=1>
  <h1 aria-level=4> level 4 </h1>
  <h1> level 2 </h1>
  <h1 headingoffset=20 headingreset aria-level=3><!-- 3 --></h1>
</div>

if HTML doesn't have a note for this, then we can get it into html aam, aria in html, or both - and i'd assume MDN author guidance.

I haven't looked at the PR text itself yet, but I think such a note/example would be valuable.

I've added a note mentioning aria-level as well as an example demonstrating their combinations.