As a workaround I've started putting the person's username (or part of it) at the start of the Subject line.
Could someone do a quick hack to make this automatic?
So if I start a Convo the username of my recipent appears first in the Subject line up to its first 7 letters.
If I receive a Convo the username of the sender appears first in the Subject line up to its first 7 letters.
It doesn't help so much with grouyp Conversations, we still need a proper display of all participants.
But a) most or a lot of Convos are with one person
and b) it would help the memory to see even one participant displayed.