line breaks, embellished operators and space-like content

Hi www-math,

On the MathJax issue tracker
<https://github.com/mathjax/MathJax/issues/1228> we had a discussion
revolving around embellished operators and line breaks.

The example from a user was

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mtext>A</mtext>
  <mo>+</mo>
  <mtext>B</mtext>
  <mspace linebreak="newline" />
  <mtext>C</mtext>
</math>

which won't have a line break in MathJax rendering because the spec seems
to say it's one big embellished operator.

My question is: shouldn't a pure linebreak end the scope of an embellished
operator instead?

Personally, I find it odd that mtext is considered space-like.

It does not seem to meet the criteria of the spec ("typically render as
whitespace", "do not affect the mathematical meaning" -- neither is typical
for mtext). It seems even more problematic in an HTML5 context, where mtext
is one entry point for HTML mixing.

Best regards,
Peter.