Optimised way of storing threaded converstations?

I don't think there is one single answer to a question like this. It all depends on how many users, how many conversations, the hardware you have, requirements for how responsive the system should be to users, and so forth. If you can get adequate performance by not having a second table for unread messages, then that's probably the better route.

Always simplify when possible.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.