This would have to be far and away the most annoying ‘feature’ of Pidgin.
In just about every web browser, Ctrl+L is used to highlight the URL bar allowing easy navigation via the keyboard. In pidgin it’s used to clear the scrollback of the active window. As a web developer I’m always hitting Ctrl+L in the browser however every now and then I won’t take notice to which window is active on my desktop at the time and use it while Pidgin is active, clearing out the conversation I’m having with my contact at the time. Frustrating!
Open ~/.purple/accels and change
; (gtk_accel_path "<PurpleMain>/Tools/Preferences" "<Primary>p")
(gtk_accel_path "<main>/Conversation/Clear Scrollback" "")
Remember to remove the semicolon at the start of the line!