This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
by default, CTRL-D deletes the current line. to change any keystrokes go to Window->Preferences->General->Keys-> find CTRL-D and click EDIT. Remove "delete" from the list. Find "duplicate lines" in the dropdown list of actions. Click Add and then Apply