Michel,
Let me ask for an ER on this new UT collapse behavior.
The + and - are relatively small click targets, ie it takes longer to accurately position the mouse to expand them.
This isn't so bad on the forums and sections because we can click anywhere on the forum/section name to accomplish the expansion.
But with threads we can't, we have to click the + to expand the thread/subthread. So here is the ER. If the message title link would do two things it'd help a lot: 1 - like now display the message itself, and 2 if that subthread is not expanded (ie there is a + beside the message) expand the subthread.