[whatwg] Should ambiguous ampersand be a parse error?

[Peter Cashin]

HTML5 authors:

The HTML5 spec says that an ambiguous ampersand (e.g. &something; undefined) is not allowed in element content, and in section on HTML parsing, that this should throw a parse error. 

However, browsers seem to render an ambiguous ampersand verbatim, which appear to be a good thing to do.

Is the specification intended to have compliant HTML agents stop parsing ambiguous ampersands?

I suggest it would be better to amend the specification to say that HTML5 agents "should" accept an ambiguous ampersand and render the text verbatim (as plain text characters), rather than throwing a parse error.

Is there a historic or technical reason for the specification wanting to treat an ambiguous ampersand as a parse error?

Peter.