The quitting action in konsole is named "Close window" instead of "Quit". This is slightly inconvenient: for instance, if one sets a new shortcut for quitting applications (e.g. Meta+q), konsole will not respond to it, unlike kate, dolphin, etc. I assume this is a bug, although I guess it may be a design choice. Also forgive the poverty of the bug's explanation: I have no idea of how an action and its shortcut in the kcm are bound to applications.
Due to Konsole being a terminal, all the Ctrl+keys are sent to the terminal. Konsole uses Ctrl+Shift+Key as a replacement. So Ctrl+Shift+Q will close the Konsole window. If I recall, we use "Close Window" instead of "Quit" since all open Konsoles use the same main process id. Does this answer your question?
Right, what I had imagined was that an application specific setting would override the kcm setting for an action with the same name (clearly I may be wrong about this). Hence shipping with "Quit" set to "Ctr+Q" in the system settings wouldn't impact the "Ctrl+Shift+Q" setting in konsole. Users though would still be able to set an alternative shortcut, say using "Meta", to quit all applications, including konsole. Of course I may be overlooking some obvious problem, and as I said, I may be wrong w.r.t. the ways conflicting shortcuts are handled. That said, I'm perfectly satisfied with the answer based on the fact that all konsole windows share the PID. Thanks for taking the time to answer what is really a nitpick.