I&#x27;ve always used this intentionally in spite of being fully aware that it&#x27;s &quot;ungrammatical.&quot;  Saying that singular they is ungrammatical is rather like saying that irregular verbs are ungrammatical or uncountable nouns are ungrammatical.  It doesn&#x27;t matter because there are already a significant number of irregularities in English and having one more isn&#x27;t going to cause any problems and, relatively speaking, isn&#x27;t going to make English any less systematic.