When we are replying to someone through gmail, the whole mail sent by person is getting quoted. But gmail is powerful as many features are unknown to users. This is 1 of them. Instead of getting quoted whole previous mail,You can select particular text you want to send as quoted string.
Before replying to mail, select the particular lines of mail you want to see as quoted shown below.
Then click on reply button. You are done with it. Now only selected lines will appear in reply mail as quoted message.
(1) One can highlight to receiver that for which particular lines of message you are putting emphasis.
(2) Length of mail appears small.