There is always a lot of debate about rules in Warhammer. Some of it is justified; it's hard to make up a rule system that will work across thousands of gaming tables. The rules governing wargames as opposed to a computer game have to be much more flexible to account for the creativity of players. My friends and I often play custom games of 40k.
But the main rule set is designed to allow players to meet total strangers and have a common understanding of the game. This is where rules problems come into effect; A miss understanding or different interpretation of the rules can not only bog down a game but ruin players fun.
The common way to resolve rules problems is the "Rules as Written" method. RaW seems like it should be the be all and end all of rules settlements but there is a massive problem with it; The players themselves. Being a competitive game players are always looking for advantages. The worst players are the ones who use the rules as a weapon. They often will quote little loop-holes and weird order of operations arguments to explain why you can't or they can do an action. Things like
"We are playing a 750 point game and I brought my Black Templar but I didn't want to use the lame Emperor's Champion model so I only brought 749 points. My codex trumps the rule book and it says ARMY"
Now whats wrong with that argument? The logic is fairly sound.
All Black Templar Armies that are 750 points and higher are armies that must take an Emperors Champion
All black Templar armies that are my army are Not Black templar armies that are 750 points and higher
All armies that are my army are armies that do not need to take the emperors champion
While the logic is sound the wheels fall of this particular argument have nothing to do ether premise or the conclusion. It's the Ethical implications within the argument. What the argument is really saying is;
"I want to use an option that is superior to the Emperors Champion; I am going to fudge my numbers so the Emperors Champion isn't required by the rules as is exactly written."
Another why to say this is "I am going to do what I want to win and fuck you."
The simple truth is that Wargames are supposed to challenge players on the table top. Players are supposed outwit each other using the models on the table. You're supposed to take an army and maneuver it to victory above the table play is reprehensible. When players start looking for exploits and work arounds to stack the odds in their favour they are actively ruining the game. If you are playing the game in a way where a lot of people argue with you; chances are what you’re doing is wrong. It may not be wrong by some stretch of logic. But it could me wrong a morale level.
A personnel example I have of this type of behavior is a player trying to keep Abaddon from joining a unit of Plague marines. The argument being that while having the mark of chaos ascendant Abaddon had all the Marks of chaos. But the rules say a model may join a unit with a different mark. There was an argument for both sides (since remedied by way of FAQ) but he wanted to win so he argued until he was blue in the face that Abaddon had to be “on his own”.
Keep the battle on the table. Resist the urge to try and use the rules as the decisive weapon in your list.