I find the medium to not lead to productive dialog. The only interesting posts I've read are ones where someone essentially ignores the format and writes a long form comment over ten serial tweets. Limiting people to 140 characters (or 2x that now) leads to people spitting out punchy comments that lack any nuance. Rather than a dialog you get either echo chamber if the participants are in agreement, or if the participants are in opposition, a series of tweets attempting to land a body blow on the other.