I would say the work isn't "fair". For every alt account someone enrolls in a campaign on the forum, the brainpower of their posts are reduced in half. So if someone enrolls 4 accounts, the IQ of each post is only around 25% of what it should be.
It comes back on why did campaign manager pay the post if the post quality is way below the standard.
Wrong. It comes back on you trying to excuse dishonest behavior, most likely because you yourself engage in it. And you are not the only one. The campaign rules are in place. Breaking them secretively is an act of dishonesty. I would not trust such accounts in any type of situation.
What’s the difference for user having 2 accounts to user with 1 account that post equivalent post per day. For example LoyceV average post per day is 10 post, will his IQ will be lower if he distributes that post count to 2 account?
If he starts cranking out 20 posts per day, then yes, I would say its likely the effort expended in each one would only be half as much as normal, and it would be evident. Lucky for LoyceV he's a pretty smart guy. But I don't think he would enroll secret alt accounts into the same campaign, because again, he's not dishonest.
I’m only saying that if such low post is the main issue on multiple account, why does it receive payment.
As has been explained to you a couple of times already, there's more to it than that. Its also about giving multiple people the chance to earn money from being enrolled in a signature campaign.