Mail.app has a handy feature that lets you only quote a specific section when replying to an e-mail.
To accomplish this, select the block of text you want to quote:

Click reply and you’ll have a new message with only the selected text quoted:

This is great when CC’ing someone without showing them the entire e-mail–only the part you want them to focus on.
Thanks Matt Jones for submitting this tip. Check out our other Mail Tips.
Steve Jones
Not sure how I could have messed it up; it's too simple. Does this work for everyone else? April 25th, 2008 at 3:01 pm
Jerry
Concetta
I thought it would, since I do this all the time, and have been doing it back as far as I can remember (pre-Leo)
10.5.2, Mail 3.2
Strange.
Can't figure out what your deal is either! April 25th, 2008 at 10:51 pm
Concetta
go to your Mail prefs, to "Composing"
Do you have "include all of the original message" checked, instead of "include only the text selected"?? April 25th, 2008 at 10:54 pm