Implications of Illeism
Booker winner Anna Burns mentions "ear bashings from those who speak of themselves in the third person plural." Referring to oneself in the third person is called illeism. Except in young children, it's considered egotistical, unsavoury, even pathological. Chris Bourn gives some background and a dissenting view. But these discussions are about third person singular. Only the Queen can call herself we, and that's just a quirky historic precedent.