There are actually social frameworks in place to compensate for both of these, but what passes for modern internet culture has largely rejected them.
Um. By which I mean to say:
Dear grzm,
Thank you for your recent post on HackerNews with regard to the limitations of empathy in a text based medium. I largely agree with your points.
However, I would like to draw your attention to an existing practice, specifically intended to compensate for the drawbacks you mention; this is the traditional letter-writing style. A fixed communication structure provides social cues which compensate for the lack of emotional side channels, as well as providing continual reassurance to the reader the communication is, in fact, desired.
Of course, this is not a panacea (indeed, it can be abused to great effect: I highly recommend reading some of the correspondence of Mark Twain!), but I am of the opinion that it can be effective in facilitating communication between people of differing opinions.
Thanking you for your attention and in anticipation of your reply, I remain,
Your sincerely,
david.given
PS. It's a been long time since I had an excuse to use the word 'facilitating'. Also, I had to look up the closing salutation. I also suspect that one of the main reasons this worked is because it's substantially more work. Tossing off a dismissive note in a couple of minutes is one thing; sitting down with a pen and composing a proper letter means you have to think about what you're saying.