Doesn't matter that much. Well constructed one liner can be more useful and constructive then a multi paragraph text. Just write as you would tell it to your friend, don't overwrite and don't chase merit, just keep it simple and straight on point.
I haven't seen a one-liner get any merits up until now, no matter how good it was. Maybe people are inherently more inclined to reward longer posts, because they imply that the reader knew what they were talking about?
Which leads people to draw things out, since merit is the most important thing for them right now.