There are two aspects to any written debate which I think need to be considered in any discussion about readership styles.
Firstly, written debate is is relatively permanent, so what we say has a habit of being read and re-read - and quoted back to us after our position has changed through debate!
Secondly the audience is invisible.
Let us transport ourselves to a university debating chamber, where someone might say 'What's the problem with that idea then pal?", said with a smile and an arm round the shoulder it's seen as a quizzical search for more information, if the "Pal" is spat out when standing square on shoulder to shoulder with faces inches away from each other and red cheeks, we see a different image and a different intention.