I also remember a story in SWTOR about a Jedi who got cut off from the lightside of the Force by a Sith, forcing him to use the dark side instead. So it seems possible.
I actually had to do a quick visit to the wiki for this. From what I gather, Nadd did not use Sever Force or any related ability. He used his command of the Dark Side to break the connection Exar Kun was trying to establish with Master Baas. Kun was still connected to the Force, but unable to save himself from the spirit of Freedon Nadd.
Do you know who the Jedi and Sith were, as it will be easier to judge exactly what happened if we know. The Jedi's loss of ability could have been the result of the Sith's overwhelming power of the Dark Side, or the Sith could have used the Dark variant of Sever Force as Nihilus had done to Traya.