Jess and Milo play fight all the time, if Jess hisses then Milo will stay away (this has only happened a handful of times in 3 months), there is alot of batting with paws and pinning down and kicking but I feel they are just playing, sometimes my Hubby gets a bit upset by it and tries to break them up I tell him to leave them to it, I think Milo is just being a kitten and playing and Jess is being the boss and telling Milo that.
I don't think we've ever had a full on cat fight, but sometimes its hard to know what to worry about