Unless I'm much mistaken there's no option to disable the quick look (press space bar to see details on the torrent). In the most recent version (2.12) a change was introduced whereby the quick look will display in the file selection screen when space bar is pressed. What this means is the user can no longer press space to easily select a file they wish to download from inside the list, use the arrow keys and continue to quickly select the required files. The initial file does get selected but a useless quick look gets displayed and the focus is removed from the file pane, requiring clicking back into the pane to gain focus and continuing selecting the files with the keyboard.
This was a pretty silly move and as such I've rolled back to the previous version.
Hopefully this can be amended in an upcoming patch. Thanks.