If the topics chosen are VERY careful, I think it can work.
The issue is that it will discourage some from commenting at all, because they may not really want to get into a long issue (and are worried that specific statements might encourage responses they don't want to get into).
I think instead of "argument", which implies something more formally Aristotelian, it should be "a point of contribution". That could be a comparison, a metaphor, a poem, anything that wouldn't be a formal argument but (aims to) elucidate.