+> This is really a separate feature request: copy non-`<a>` markup
+> in headings into the TOC. I don't think this necessarily makes
+> sense in general. In particular, any `id` attributes on child
+> elements must not be passed through because that would make
+> the ID non-unique. --[[smcv]]
+
+It seems you can stuff anything into ordered lists (according to w3.orgs doku), so apart from stylistic reasons and suboptimal display of links in headers (see below) I don't see any problems with markup in the toc.