Is it common practice for managers to take your notes after the interview?

Hi,

Yes, in fact I have done the same today when I interviewed upcoming interns. The main reason is that interviewers typically have 2 3 different cases, thus they don't want you to share the solutions to other applicants. 

Best,

Deniz

Hi,

Yes, that's totally fine. They want to keep the cases confidential. 

Best

Yes, we do that. The simple reason is that we don't want interview cases to be documented & distributed among potential candidates.