I think that if a candidate has made it through your entire process, that you already should have a good read on them and trust them essentially. If you decide

I think that if a candidate has made it through your entire process, that you already should have a good read on them and trust them essentially. If you decide not to hire them and they write you a note thanking you for the process, offering you some feedback on your interview process (positive and improvements) and ask if there's anything they could focus on over the next year or two that would make them a stronger candidate, that it's pretty clear they aren't going to fight with you. And yes, I do think you lose the opportunity for someone to reapply to another open position (or refer their friends) which is a shame, because presumably you thought this person was a /strong candidate/, they just didn't quite work out at the end for some reason.