Try replying to the original post that is being replied to i.e. where the subthread starts and it should add to the bottom of it, not perfect I know. Maybe needs raising with ning
I suspect it will make the threading even worse. Are we hitting some limit on the nesting depth - the reply links seem to fall off most frequently on deep conversations?
Definitely worth pinging Ning - they're not going to get better unless we tell them about the problems!