How is a student-teacher dating relationship moral/ethical/morally legal/GOOD?

the fundamental ethical issue is exploitation and power differential. When you're talking about a student who's a minor, there is no way to support that side of the debate. So move it out into adult teacher with adult student (grad school). That way you can shift the argument safely onto consenting adults /adult judgment. Still need to address the power/exploitation risk (date once the student is out of the cl, transfer grading to another teacher, etc.). As for the affirmative side, you can take the approach of two adults sharing a research quest, each energizing the other, and because they share ideas so easily, really creative thinking flows. Like minds supporting each other. Less pressure to balance work and play, since they're already intermingled. Think mentor ~muse.