Erratum 3135 is "held for document update" which is not the same as "verified". The original text in the RFC still stands until it is superseded by a revised RFC ("any future update of the document might consider this erratum, and determine whether it is correct and merits including in the update" - http://www.rfc-editor.org/status_type_desc.html)

Also, erratum 3135 is against RFC 5322. But in RFC 5321, it still says

````
Local-part     = Dot-string / Quoted-string
Quoted-string  = DQUOTE *QcontentSMTP DQUOTE
```

So, however barmy this example might be, it is still allowed by RFC 5321 and I think it has the correct category.