Basic Rules
Every Friday I go to my LGS and play commander with the pods. The players in my area have all grouped together and created a variety of quite decent decks through trades among each other or purchasing cards.
I have gone up against a mono blue [[Sai, Master Thopterist]] several times piloted by the same player. The player has all the best staples in the deck and it goes quite well. And I now see it, because he doesn't know the basic rules of magic and some of the cards are not being played properly, causing him to spiral out of control with the deck and usually win. Until I played against him a few times.
In the first game Sai was on the board and he cast [[Virtue of Knowledge]]. I watched as he cast another artifact and then proceeded to make (2) 1/1 thopter tokens.
I said, hold on a second. The enchantment doubles ETB effects, not cast effects. I wondered why he played it, but didn't want to assume. He was sitting beside our LGS "Best" player and even he didn't understand the situation of why the enchantment didn't work.
I explained that cast triggers and ETB triggers are entirely different. The artifact being cast triggers Sai, but it does not make another thopter because the artifact entering does nothing. (With the current board state).
They both resisted my explanation and I calmly explained it again. I said the thopter is created on the cast, enters, then the artifact being cast resolved.
In the second example the same player, with the same deck cast [[Drafna, Founder of Lat-Nam]].
They had a sol ring on the battlefield from a few turns prior. They used Drafna's bottom ability and attempted to copy the sol ring that is on their field.
I said, hold on a second.* The sol ring is already on the battlefield and no longer a spell, it is a permanent. Drafna clearly says copy target artifact spell you control.
And again, I had to explain the basic rules of the game to a seemingly prodigious player. I showed them the first ability of Drafna is to bounce an artifact back to your hand so that you can copy it. Specifically because it doesn't tap Drafna to bounce the artifact.
But they still didn't understand until I explained it three times, this Basic Rule #1 of how a card isn't a spell in certain areas, and it being a permanent now, etc.
So now I feel like this guy's deck is being abused quite heavily without the pilot understanding the core rules and restrictions of the game.
I have heard several instances of this player one-siding tables. Maybe now I know why. Hope this helps explain the scenarios I've encountered. Just some information to share.