Slapsies??? That's cute. I've never heard it called that.
Here we call it "bite face" or my favorite ... "snake neck".
Anyone else call it something different?
Our BO had the same problem as you....and sometimes the boys would get some nasty facial wounds....she just seemed to take it in stride. She said they were just playing......still, they were hurting each other bad enough to leave facial scars....
She didn't tolerate kicking though, as some of them were show horses and she didn't want to risk injury. She did seperate them from time to time....especially during show season.
Other than the kicking her show horse, she didn't care about the wounds.
Personally, I would not like it....and we are facing a similar situation to you but on a lesser scale. Our gelding is always biting our mare's butt....sometimes taking off bits of hair, and once scraped off some skin.....
I don't like it much...and if it doesn' t stop or if it escalates, he's going into a seperate pasture.