What is your system details / Desktop Environment. I use Cinnamon 1.8.8 and the scroll wheel moves the chat window text by about 5 lines, not the full window.
Hmmm. Now that I played with the window size, I cannot reproduce it anymore.
Closing pending the problem coming back.
Scrolling in the store page (or other pages) with mouse wheel flips about 15 lines. Flipping 15 lines is too much. 5 lines or 3 lines should be more appropriate.
Nothing extracted yet.
It scrolls exactly the size of the window now: if the bottom line is half-visible, after scrolling only its bottom half will be on the top of the window. Mouse wheel should only scroll about 3 lines.