It is such a loaded subject, Eiko. I would say that there are many potentially unethical things that can transpire between students and faculty (also depending on the field.) Most often, the boundary crossings happen in another direction - simply because faculty have more power.

Current teaching evals fulfill the role to valididly and reliably measure 'teaching quality' (and fail at doing so, arguably). The construct 'unethical stuff' isn't part of the 'teaching quality' construct imo. I would measure this separately.