id namespacing is undocumented and seems to be broken

[gibson042]

The namespace attribute used in test/baselines/sources/namespaces.html is not documented at https://tc39.es/ecmarkup/ , and rendering that file generates many unexpected warnings and in-document links.

[bakkot]

It's definitely inadequately documented. It predates me, but my understanding is that namespacing applies to terms and definitions within the namespace, not to ids - ids are an HTML concept, not an ecmarkup concept, and must be globally unique within the document (not just within the namespace) so they can be linked.