I can't imagine that this makes any sense.
Let's say you give every interviewee feedback:
- 90% of candidates will be grateful
- 10% of candidates will not like the feedback and start to argue (at this point ignoring emails might make sense to avoid wasting time)
- 0.01% of candidates will actually sue you over it
The lawsuit will probably go nowhere, and in the worst case cost €10.000 in legal fees.
But all the good will from the other people must be worth something! Maybe one of all those people who you gave good feedback refers a friend, and they apply to your company. If you hire that person, you just saved 10.000€ that you don't have to pay a recruiter!
So either all these lawyers are giving bad advise, or maybe my numbers are wrong? I've never heard of a lawsuit where a candidate sued a company as a consequence of interview feedback that they got, so I assume that must be a very rare occurrence.