The honour code you refer to isn't really in the movies. They show the Predators are out for sport, not honour - again, Dutch says there's no sport in shooting Anna, and Keyes likens them to big game hunters, not honourable warriors. There's nothing honourable about shooting someone in the back.
Again, I would say you're falling into the trap of fitting everything into your version of honor, and not theirs. I challenge you to try to get out of your own headspace and into theirs. Even how honor is perceived and acted upon in some parts of the Middle East could often challenge your ideals. But it's honorable or dishonorable to them.
The honor code has always been the intent
of the Thomas Brothers and to me it has been 100% depicted. The Thomas Brothers explained Predator 2 is the "bible" for the Predator character.
To the creators, the Predators are a race of sports hunters. They do have a system of honor and code, per them. Like American hunters believe they have honor, when they go to church on Sundays after slaughtering defenseless animals with high powered weapons in camouflage on Saturdays.
You may question hunting deer or bear from trees in camouflage clothing using high powered scoped rifles ... "They don't fight fair! Where's the honor in that?" I do too. But to an American Hunter, it's not a question. The kill during the day, and kiss their children goodnight, living "honorable" lives. If the deer could reason, I'm certain they would see human hunters as psychopathic killers, even if they follow a code by not shooting the young or pregnant. So it is important to get out of your headspace, and into theirs.
This intent made it into the film crystal clear, especially when not just the Elder, but the whole tribe
spared Mike Harrigan after he killed one of their own... and they even rewarded him for it!
It was crystal clear in the film when an armed
trained police officer Leona was spared from being killed because she was pregnant.
Some to me ridiculously argue that it's some sort of population control, even though the intent, even though it still qualifies as an honor code regardless... but by what Peter Keyes says in regards to how little Predators visit our planet, I don't think Predators will have to fear that killing one pregnant woman armed cop would impact the survival of the human species. It's following an honor code, i.e. their standard of conduct, any way you look at it.
Sparing the child in the cemetery. Sparing the unarmed. Sparing Anna if it's perceived as sport or not is still following a code. Even finding Dutch worthy enough to challenge him in weaponless combat, is all depictions of an honor code. Get into that Yautja headspace y'all!
Even, in regards to the detonation, I see that as the Predators do not want their body or especially their tech discovered. The devastating impact of leaving that behind would be so much worse than any unwanted deaths it may cause in its radius. - It's like when humans hunt bears with spears, they bring along a gun just in case. Because after a point, it gets to a point, where all bets are off
City Hunter is quite a psychopath.
He was definitely written as reckless and a rule breaker. You might like this. I wrote about it here, and hope to eventually turn it into an article someday soon! https://www.avpgalaxy.net/forum/index.php?topic=61579.0