TLDR:不允许.
我在这里找到我的答案:
Permitted parent elements for h1: Any element that can contain flow elements,
hgroup.
资料来源:https://www.w3.org/TR/html-markup/h1.html和https://www.w3.org/TR/html-markup/th.html
解决方法
HTML living standard表示禁止这个.
@L_404_3@内容模型如下(重点增加):
Flow content,but with no header,footer,sectioning content,or heading content descendants.
“Heading content”是指h1,h2等元素,以及hgroup元素:
Heading content defines the header of a section (whether explicitly
marked up using sectioning content elements,or implied by the heading
content itself).
h1 h2 h3 h4 h5 h6 hgroup