Geez, First couple of posters are a bit heavy! (IMO) Made many friends with students when I used to instruct. Still in touch with quite a few though I live hundreds of miles away. Personally I can’t see how forming friendships has any detrimental effect as long as you instruct well.
I feel that on a romantic level you have to be very careful. Students give a lot of trust to their instructor and it can be easy to handle the situation very badly.
Just my opinion.
LF