The deal about the polyester melting (as it was explained to me) is that if it melts on the skin it will stick to the skin creating a worse burn where as cotton turns to ash and can be brushed off - less severe burn.
I believe Jan is right about the hotness of some batting. When my boys were babies I always did layers rather than one thick item.
I always wondered about the distance on quilting versus tying. If it bunches up when it's not quilted close enough there's a lot of area not secured with tying.
I like flannel because you just need to anchor it. I also like to tac it with my sewing machine if it's a small quilt rather than tying it.