Do we need riding skill to do mounted combat?

I know this sounds like a silly question, but my Hobbit Hunter never bothered to get riding skill as I roleplayed her as hating horses and walking everywhere. Does she need riding skill for War Steeds and mounted combat, or just for riding ordinary horses?

Also how does mounted combat affect Hunter Traps? Are they converted to slows rather than 'rooting' mobs, like stuns and dazes?