The Commonmark spec says for HTML blocks (rule 1), that
<pre , or
<style tags should start an HTML block and not be terminated until the end tag is found.
Although not specifically markup,
<textarea> should be included in this rule because it is a multi-line element. If you include a multi-line textarea the rendering will break the contents in the textarea.
If this shouldn’t be included as a spec change, I’m curious what the alternative would be since it seems like Commonmark is basically a superset of HTML.