Thanks for following this strange tale.  As you noticed, everyone has mixed motives.  Severus is cool, but there is no escaping the Ministry's desire to accuse those involved of wrong-doing.

Severus recognizes the pair as agents who will try to get him to incriminate himself.  He professes no personal interest in a threatening public school.  The outrageous behavior was the Black sisters tricking the other agents, and Severus pretends ignorance.  His plan, however, backfires since the two agents list him as a pureblood conspirator because of his preference for quality tea and biscuits.  The scales and feathers refer to his recurring dream - once again, he has been judged.  Severus almost distracts the younger agent by offering him a chance to copy Cormac's outfit.

Thanks.  Glad you liked the Severus episode.