From https://gitlab.com/gitlab-org/gitlab-ce/issues/35782

<div data-test-id={{user.id}}>
  {{user.username}}
</div>

Everything from the ending > on the first line to the {{ on the 2nd line is marked as invalid syntax.

{{user-model onSave=(action 'afterSave')}}

the parens around the action helper are marked as invalid

{{#user-model as |user|}}
 {{user.username}}
{{/user-model}}

The |'s around user are marked invalid