Not taking names, but there was one guy who abused a glitch to earn 7 cores each for every dismantling of a weapon by acquiring it over and over without any cost or effort, and he is abusing it to masterwork everything he owns.
That's pretty unfair for the people who don't abuse it.
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Bungie has been aware of this bug for a while now, and have disabled the ability to acquire pinnacle weapons until it's fixed. While you could say it's unfair, Bungie does not issue bans or restrictions for finding exploits within the game.