Hard to master. somewhat easy to learn. Its more than glide tossing banana around. Mind games is also part of it. imo
Though the post above me + are right. Everyone nowadays pretty much know how to either: Counter Diddy or just know how to play against him. Correct me if im wrong.
You're pretty correct with that statement Diddyknight. After the whole Ninjalink thing happened everybody started going, especially MKs, "We need to learn everything we can about Diddy since he can actually be a threat now" Not to mention they had plenty of practice because people started to flock to Diddy as an answer to MK so the MKs were all like "Oh **** noez. We're Super Saiyans *******" and the Diddys started losing again. Except for NL. He's the heard virus that can kill Goku.
Metaphors and comparisons aside. Diddy is easy to pick up when everybody playing is a noob because they don't deal with bananas. Then the opponents get smart and shield and pick up or make it where you can't get to your bananas. So the diddy starts doing things like glide tossing and dribbling. His opponents are like mind-blown and stuff. So he's whooping *** for a few weeks until one of his friends realizes that to beat glide tossing, all you have to do is use the same thing you were using earlier. Just faster. So they start rushing harder and playing keep away better and they start using your bananas against you.
Now the Diddy can't rely on his bananas on as much so he to learn some other ATs with other moves. The only thing is no matter how useful barrel cancel, Diddy hump>footstool, Barrel Spiking are. They can't replace the fact that the main AT for his bananas, Glide Tossing, Just got owned. So he has to learn a few other banana ATs which won't really make the same impact as Glide tossing.
Then something happens. The Diddy player learns about 2 things. Spacing and Mindgames. And all of he sudden he starts thinking...I can glide toss. I just can't auto-pilot, As Vyse so nicely put it, or be stupid. So then the glide toss comes back into play but it's smarter and therefore Diddy is once again a threat because the only way you can beat good spacing and mindgames is with better spacing and mindgames. No technique in the game can defeat that. From the most basic techniques of shield to the most advance.
(Holy **** I wrote a lot. Wall of texts for the win?)
For those who TL;DR Diddy is hard to master because his bananas have to be used in conjuction with spacing and mind-games, some of the hardest things to learn in Brawl. And everybody knows how to counter a diddy who doesn't use those 2 things.