1757374:How's Curse of Fiend's restriction clearly part of the effect?
Because of the fact that activation requirements are the first thing stated on a card's effect text, like discarding a card or paying X amount of life points. The fact that it's the last thing mentioned on the card implies it's part of the effect. Meanwhile, Cold Wave's effect text implies that it being the first thing you must do in your Main Phase 1 is an activation requirement, which Diamond Dude supercedes.
The argument is whether or not Cold Wave's first sentence is an activation requirement...nowhere in the rulings does it say Diamond Dude cannot override timing requirements; the Curse of Fiend ruling can easily be interpretted as its timing requirement is part of the effect, which easily explains why Diamond Dude doesn't allow its effect to activate
JD DeKeyzer
-YGO R&K LV2
-PM LV1
-TO LV1
-inventor of the world's first Duel System (Duel Terminal's a cheap knock-off of this, I swear)