No matter which university it is, teacher-student romances are prohibited.
If discovered by colleagues or supervisors, it will definitely affect the evaluation of academic titles and promotions, but how would people find out?
In fact, it's quite difficult. As long as the two people involved are careful, avoiding intimate physical contact in public settings, they won't be discovered. Even if someone notices they have some undue physical contact, they can just deny their relationship with a unified story, leaving the management in a difficult position to insist otherwise.
So, unless for some reason the two of them have a falling out, usually it's the student who feels deceived and reports the teacher to the school, making a big scene before the school takes action against the teacher.
In detail, this is a case of "no complaint, no investigation" problem.
