Copywriting is communication. Your reader might be in a different country, on a different time zone, with questions you’ll never even hear, but that doesn’t mean you’re not communicating with them. And just like in any conversation, you need to talk like a real person. If you start using an arrogant tone, or throwing around complex words, or rambling on and on about nothing in particular, it’s only a matter of time before the customer looses his/her patience and moves on to someone else.