Having served on the resident selection committee as a chief resident, I can tell you that most likely a decision on whether to rank someone or DNR (do not rank) has been made at the end of the interview date.
A composite score is given for an applicant based on parameters such as credentials, previous experiences, liklihood to succeed, personality, interest in the specialty..etc.
We rank applicants based on the composite score regardless of whether the applicants come back for a second look or not, or if they tell us how much they like us. It is usually irrelevant.
Still, a polite thank you note after the interview is still expected for courtesy.
Occasionally for those highly qualified applicants, we'll go out of our way to let them know that we're interested in them. But this doesn't happen a lot. Some programs do this all the time as a routine.
And we go from there...waiting for the results.
All in all, the NRMP is a joke. It should be like college or fellowship application process where you just apply to places where you think you want to be and hopefully you'll get interviewed and end up with multiple acceptances so that you can decide what is best for you.
Just my 0.02.