Users have better things to do than constantly click "report spam" buttons on minor variants of the same content a million times in a row. People see spam reporting as equivalent to filing a complaint i.e. the company failed and they're informing it that it needs to do better.

Automation detection and privacy are orthogonal. The ideal bot detector yields a single bit of information: bot or not. It doesn't need to try to de-anonymize users or anything like that. As for UX, well, spam is a bad UX.