Well, it's all in the subtext between the characters really. Basically, any chemistry or subtextiness between any character on the show is going to be paired off one way or another by someone in fandom, and the Mohinder/Sylar is just the starting point. There's LOTS of HoYays in Heroes, let me tell you (Mohinder/Sylar, Nathan/Peter, Peter/Mohinder, Bennet/Matt, the list goes on) ;)