Undo on Command+L would be of no use except for people pressing buttons before thinking. That needs to be corrected to, "think first, THEN press buttons." :)
Which goes in front collision course with the usability principle "Don't make me think" for designing great user interfaces
Incidentally, that is not what "Don't make me think" refers to. That phrase refers to software's ability to _guide_ the user to the discovery of _how_ to command the software. The goal of the UI is to establish a low-level "connection" that the software feels like an extension of the users fingers. Modal pop-ups ruin this. I see you came around to understand what Cmd+L is all about later down in this thread. Good! Because I thought you were about to say, since Cut and Copy could possibly "lose" valuable code in the paste-buffer, they too, should be guarded with a modal confirmation pop-up. ;-)