Well if I'm the reason for banning Marks, for either being honest or having more Marks than I have trophies then you'll have to ban either of these two. Fact is there are numerous glitches/exploits and even more people that have cards obtained through them (I know only few examples but refuse to believe I'm the only one to ever discover a glitch like the one I found, especially since I wasn't even looking for it). Every person who got a Mark card through spins in the past got one through a glitch: Mark cards weren't supposed to show up in spins back then. Will each of them be prohibited from using them in any forum event? As long as it isn't prohibited one can't blame them for using them and being honest, right? One can have all nymphs upgraded and unupgraded and just claim to be lucky, as unlikely as it may seem it's not impossible. I could've claimed I got all these Darkness Marks from spins back when you could win Marks from spins. As unlikely as it would've been it would not be impossible.
So one has to make a point here, do you want to ban Mark cards, or ultra rares like Nymphs, that people aren't supposed to have based on the number of trophies, or based on the story they have on how they obtained them? I for one think the latter is complete nonsense since honesty should always prevail. Just because one is a good liar doesn't mean one should have to lie to be able to use ultra rares, regardless of how one has obtained them.
But go ahead and ban just me from using those Mark cards in PvP events if I'm to blame for telling the truth. No one else has told anything similar and shouldn't be banned from using them because of me, no?
Finally, I'll use a hypothetical story to question the limit of usage of Mark cards based on trophies. [sarcastic rant]
Say someone, let's call her X, has 3 trophies. X really wanted 2 Fire Nymphs and never got them from the oracle, hence X used 2 of these codes to get Fire Nymphs. Using the third code X gets a Fire Mark since X really likes Fire. Next, through some glitch X gets 2 more Fire Marks and uses them. X simply claims these Fire Marks came from reward codes rather than from the glitch, and that the Fire Nymphs were from the Oracle. Everyone believes X, after all, everyone chooses Mark cards as their rewards and no one ever lies on the internet. [/sarcastic rant]