Chat mode for private messages

I suppose it can be good if private messages will be organized like separate chat for the whole conversation with each member which contains all messages from this member. Right now I see several discussions even with one and the same forum member. Or at least it can be good to add some filter there to filter only the different discussions with some particular person. I have already wrote something about chat mode for topics but this issue is a bit different. Though chat box for writing private messages (mentioned for topics earlier in my previous feature request) can be useful and comfortable also. I can divide some points from this overall feature request to several topics if necessary, maybe I have mentioned too much in this particular topic.