Is it possible to give too much praise in a reference letter that supports a green card application? I am currently writing a reference letter for a colleague applying for a US green card. Given that I don't know much about the process and expectations of the immigration bureaucrats who will handle the application, I asked around for examples of such letter. Obviously, they are all glowing, and I started writing in the same style.

Now, don’t get me wrong: she is truly a great researcher, I wish her the best of success with her application and hope to help as much as I can (at least, not to let her down). But… at the same time, as I finished writing my letter, I wondered: is it possible that I went over the top with praise? Is it even possible, in such a case? And if so, how can I tell? I mean, I did not  write anything factual wrong, but if read very literal (and outside context), it might sound more like the eulogy of a Nobel prize winner than the recommendation of a mid-carreer researcher (even a very good one).
Letters written for a green card application are very differently structured to letters written for other purposes. As was explained to me when I went through the process, the structure of a green card letter is usually 


I am awesome
here are all the ways in which I am awesome
because I am so awesome, you should trust me when I say that this person should get a green card
and oh yeah, they're pretty awesome, which I can tell because I'm awesome. 


I'm only slightly exaggerating here. The point is that GC letters are not read by academics - they are read by lawyers who don't evaluate technical skills so much as achievements and strength of recommender. So there's no way to go over the top really.