formal A person who takes part in a dialogue or conversation.
If Lexico says some word is "formal", then it means it's formal AF (it flags them as such much rarer compared to, say, the Longman dictionary). I don't want to pose as some aristocrat without a reason. How can I express the same idea using everyday language? Don't suggest 'speaker', it doesn't fit (it's only applied to spoken speech, as I understand it, I need a broader term).