While men DO nod to show agreement, if a men is particularly attuned to body language or tend to be more empathetic, he'll be more likely to nod in encouragement in the same way that a woman would - I know I do it quite often (thanks to Why Men Lie and Women Cry).
If a man is already nodding along in encouragement and you want to know whether he's being encouraging or agreeing is to look for a cluster that I've observed.
The eyebrows will raise, the eyes will look off (often to the upper-right) and the lips will be slightly pursed. This shows that they are actually thinking about and considering what you are saying. This is often accompanied by a head tilt and a slight rhythmic nod.
It may not be a universal, or even common cluster of signals, but it's something I've observed a lot in interviews, particularly after answering a question in a surprising or unconventional way.
Have you encountered this before Danielle?