[Severity: Only concerns an example rather than normative text.]

Section 4.4.6 (The h1, h2, ... h6 elements):

# These two snippets are equivalent:
#
# [version using only <h1>, <h2> etc. and no <section>]
#
# [version using <section>]

I would not consider the two snippets to be equivalent if they produce different rendering or other behaviour affected by the DOM tree.

If by chance the two snippets, when rendered with a stylesheet h1{color:blue} h2{color:purple} are to result in the same rendering, or if the two snippets are to give the same DOM tree, then I suggest saying so explicitly, as I would find either of those behaviours surprising.

If neither is the case, then I believe the text should be corrected, perhaps changed to "have the same semantics" or "are semantically identical" (which is the language used in section 4.4.11).

Consider also adding (either here or in section 4.4.11) something that reminds authors that the two are not entirely equivalent, e.g. mentioning that stylesheet considerations might favour one of the two over the other, or adding parenthetically that the two snippets might nevertheless be rendered differently with some stylesheets.  Such a hint might be most valuable in author view, but it has some use even to casual implementors given that people treat a spec as a reference and read it out of context.  (Out of context of the HTML spec, the "semantics" of a piece of input to a program might be taken to encompass all of the functional effects of that input on the program, which would include rendering in the case of an HTML-rendering program.)