ins and del inline within a grammar production don't work correctly

I don't know if this is expected to work or being used incorrectly, but the private methods proposal has this ecmarkup with del and ins inline within a grammar production ((...) below means I've elided some further definitions there):

<emu-grammar>
  MethodDefinition[Yield, Await] :
    <del>PropertyName</del><ins>ClassElementName</ins>[?Yield, ?Await] `(` UniqueFormalParameters[~Yield, ~Await] `)` `{` FunctionBody[~Yield, ~Await] `}`
    (...)
</emu-grammar>

The resulting markup (pretty-printed a bit) is:

<emu-grammar>
  <emu-production name="MethodDefinition" params="Yield, Await" id="prod-MethodDefinition">
    <emu-nt params="Yield, Await"><a href="#prod-MethodDefinition">MethodDefinition</a>
      <emu-mods>
        <emu-params>[Yield, Await]</emu-params>
      </emu-mods>
    </emu-nt>
    <emu-geq>:</emu-geq>
    <emu-rhs a="13ccd732"><del><emu-nt><a href="https://tc39.github.io/ecma262/#prod-PropertyName">PropertyName</a></emu-nt></del>
      <emu-nt params="?Yield, ?Await" id="_ref_94"><a href="#prod-ClassElementName">ClassElementName</a>
        <emu-mods>
          <emu-params>[?Yield, ?Await]</emu-params>
        </emu-mods>
      </emu-nt>
      <emu-t>(</emu-t>
      <emu-nt params="~Yield, ~Await"><a href="https://tc39.github.io/ecma262/#prod-UniqueFormalParameters">UniqueFormalParameters</a>
        <emu-mods>
          <emu-params>[~Yield, ~Await]</emu-params>
        </emu-mods>
      </emu-nt>
      <emu-t>)</emu-t>
      <emu-t>{</emu-t>
      <emu-nt params="~Yield, ~Await"><a href="https://tc39.github.io/ecma262/#prod-FunctionBody">FunctionBody</a>
        <emu-mods>
          <emu-params>[~Yield, ~Await]</emu-params>
        </emu-mods>
      </emu-nt>
      <emu-t>}</emu-t>
    </emu-rhs>
    (...)
  </emu-production>
</emu-grammar>

You can see the current rendered result here.

There are two issues:

1. The del element was retained, but the ins element was removed.
2. When rendered, the current CSS shows the del element with a red background but without text-decoration: line-through because of this rule in elements.css.

   a {
       text-decoration: none;
       color: #206ca7;
   }
   

Presumably (2) can be fixed by adding a del a { } rule after the rule mentioned above:

del a {
    text-decoration: line-through;
}

Looking at (1), though, the only reference to del tags I see in the source is in utils.ts, and it handles ins as well:

export function shouldInline(node: Node) {
  let parent = node.parentNode;
  if (!parent) return false;

  while (parent && parent.parentNode &&
    (parent.nodeName === 'EMU-GRAMMAR' || parent.nodeName === 'EMU-IMPORT' || parent.nodeName === 'INS' || parent.nodeName === 'DEL')
  ) {
    parent = parent.parentNode;
  }

  return ['EMU-ANNEX', 'EMU-CLAUSE', 'EMU-INTRO', 'EMU-NOTE', 'BODY'].indexOf(parent.nodeName) === -1;
}

So I'm at a bit of a loss there.

Obviously, we can change the ecmarkup of the proposal to use del and ins around the entire line:

<emu-grammar>
  MethodDefinition[Yield, Await] :
    <del>PropertyName[?Yield, ?Await] `(` UniqueFormalParameters[~Yield, ~Await] `)` `{` FunctionBody[~Yield, ~Await] `}`</del>
    <ins>ClassElementName[?Yield, ?Await] `(` UniqueFormalParameters[~Yield, ~Await] `)` `{` FunctionBody[~Yield, ~Await] `}`</ins>
    (...)
</emu-grammar>

That works, although it slightly obscures the change being made.

Is the current inline use meant to be supported?

Reproduce the inline del/ins grammar example from the issue and compare its generated markup with the rendered result. Inspect shouldInline in utils.ts and the anchor rule in elements.css, then verify that inline ins content is retained and links inside del elements remain struck through.