You might say something surprisingly harsh about them that you have to balance out to seem less aggressive and bitchy.. insert the courtesy praise to even out the insult. This scenario normally happens when a group of two or more girls are gossipping about a third party but don't want to come off too strong so as to cover their ass in case someone else is close with the person.
Erin: Yea, she looked like a beached whale- I wonder what she ate at college- small children?
(Group looks a bit shocked)
Erin: I mean I loved her hair cut and she's really nice I just feel bad cause she looked so good in high school..
Susan: Yea, you're so right but that was a courtesy praise
Posse nods in agreement