For Commonmark, HTML is just one of several possible output formats, although it is special in that most of its elements can be used within a CM document verbatim. There does not need to be a 1:1 mapping to all HTML elements from pure CM syntax, and there never has been. If <h>
got added to HTML, CM processors could very well start generating documents (or more likely fragments) that used the new element based on the existing CM heading syntaxes (prefixed ATX and underlined Setext), just as they could output <section>
s today. For that, I have suggested increased control of sectioning by repurposing the horizontal rule / thematic break syntaxes in Horizontal rules as (hierarchical) section breaks etc
----
: empty headingsection
break – continue in new anonymous sibling section****
: structuralsection
break – continue in parent section afterwards____
: visualhr
break
Anyway, if one absolutely wanted to add an explicit way to generate a <h>
element (without just using it) to CM, I think seven hash marks would do:
####### Hi, I'm becoming an `<h>` in HTML output #######
####### Me too
<h>I've always been one</h>
.
<h>Hi, I'm becoming an <code><h></code> in HTML output</h>
<h>Me too</h>
<h>I've always been one</h>