If you go back far enough, and talk to enough of the old vets. Eventually you will come up with a good definition of a HO.
2 people coming nose to nose at each other from at least 3k out (ie playing chicken) pass into range with each other guns firing. Or alternatively, a true "HO" is where two aircraft are choosing to fly directly straight at each other for a period of time until the point where they're in guns range or pass each other closely. To be a true "HO" and not necessarily just a head-on merge, they are both firing at each other.
A "hot merge" where one or both pilots have forward quarter shots in a manuver or energy fight is NOT and never WILL be a HO.
The one is a low class, low skill, low percentage move. And yes it takes 2. Either plane is fully capable of maneuvering, diving under, corkscrewing, setting up separation for a lead turn or other maneuver intended to get the drop on the guy trying to setup a HO pass.
Notice the "straight at each other" its important. Taking a forward quarter shot in the middle of a fight is NOT the same as a HO. If I just finished an immelman to come back at you, its not a HO any longer. You give me a target in a turn or energy fight, and I'll take it. Any target, any direction, any which way, any time. They are all fair game, and I won't lose any sleep about it either. You call me a HO'er for that shot and I'll call you a fool, and a dead man.
Its past time the AH community accepted that a forward quarter shot in a energy or turn fight is NOT a HO. Part of that is actually defining what a true HO is. And understanding why its a low class tactic as it takes little or no skill.