Q: I’ve heard many shiurim from Rabbi Rosenfeld where he stressed that we *never* refer to Rebbe Nachman by his name (mea culpa) but rather as “Rabbeinu haKadosh”. Why are most Breslov teachers not careful about this?
A: You should ask those who do mention the Rebbe’s name why they do it.
Chazal consider calling/mentioning one’s rebbe name an act of contempt because it indicates that the student considers himself his rebbe’s equal. Among themselves, I think all Breslovers refer to Rabbeinu zal as “Rabbeinu zal” or as “Rabbeinu hakodesh.” However, when talking with non-Breslovers people say “Rabbe Nachman zal” in order to avoid confusion and the like.
Hoped this helped.