It's on the DO NOT side of the page.
Do NOT quote rejection letters of any kind in a query letter.
NO exceptions to this rule. None.
If you think you have an exception, think again.
There's no way it will help you and it's pretty much instant rejection when I see "Agent Q at XYZ was very impressed but chose to pass because of her busy workload" because I know you are quoting a form rejection. How do I know? See text of MY form rejection on previous posts.
Here's the other thing: if Agent Q passed on it, I'm not so full of myself (despite all evidence to the contrary) that I instantly think oh lo! that slithery competitor missed the chance of a lifetime and I'm going to show her.
Nope, what I think is aha, she doesn't think this will sell.
The only time I'm interested in what other agents think about your work is when they are clamoring to read it and represent you.
If you think that's unfair, I didn't say it was. What I said was this is how it works.
Two entirely different things, and the smart querier will waste little time fretting about fair and just get on doing what's effective.