Transparency about candidates selection for a post-doc position
Rules, regulations and customs vary a lot between different countries and institutions. Generally, candidates are informed that Universities are not able to provide feedback for candidates who were not shortlisted for the role. Candidates who were shortlisted and interviewed can have some feedback, but the quality differs widely. In my experience, the most detailed feedback I received from a nordic University, containing about three sentences from the Panel about each candidate. The least useful feedback I received so far consisted of one sentence:

Unfortunately, you were not successful, because we found a more suitable candidate.

In about 1/3 of cases I received no feedback at all even when I asked for it post-interview.
I have to say that currently the post-interview feedback tends to be rather useless, and in most cases it is a mockery of the transparent approach. I suspect that HRs are just too cautious that a frustrated candidate might submit a legal complaint, and are trying to &quot;protect the University&quot; by not saying anything specific or useful.
My experience mostly covers UK/EU. As I said the situation in the US might be different.