Use standard scroll bar control
The scroll bar does not work correctly. Standard windows scroll bars have a rich set of behavior, but the custom control used in Skype is missing some of it.
Clicking above or below the thumb should scroll up or down by one page. It does not.
It disappears when the mouse leaves the window.
It changes width on mouse-over, making it harder to hit (Fitts' law)
It does at least capture the mouse.
It also needs a way to easily move up and down as I am reading a long thread. Keyboard arrows don't work. There isn't a button at the top or bottom to click and scroll down in small increments (to move down as reading). I currently have to hover over the bar, grab and hold it, and manually move the mouse up and down to move the text up and down. When the text I'm scrolling through is particularly long, small movements of the grabbed bar moves multiple pages down and is difficult to control.