Many years ago a medical school applicant told me the following story:

The student sent follow up notes to all schools where he had interviewed, usually a strategic move. However, he was very upset to receive a brusque note from one of the institutions telling him that a) he should have read their policies; they do not allow post-interview contact and b) he was rejected from the school.

I found the school’s note extremely severe – almost cruel – and I strongly suspect the post-interview contact was not related to his rejection. (As an aside, he successfully and happily matriculated at another school.) But this story is a reminder that it’s important to read institutions’ policies about post-interview and post-waitlist contact. Most places welcome written updates, but make sure to confirm before you reach out.