Since some people still seem to be debating the reasoning for picking Diddy, it's most certainly based on Deejay's iconic move, the Double Rolling Sobat.
In the Streetfighter games this move will lunge Deejay very far forward towards the enemy (especially in SF4 I remember him just flying across the screen with the ex version). Diddy is the only character in the game that has a move that's both visually and mechanically very similar to Deejay's move, so the pick to represent Deejay as a side b spamming Diddy is a very accurate reference to how Deejay was in his games (or at least way more accurate then just using a character that kicks).
Of course change the spirit since it's clearly a problem that shouldn't have been made, but making the argument that the reference is weak in the first place is very ignorant as well to the source material.
In the Streetfighter games this move will lunge Deejay very far forward towards the enemy (especially in SF4 I remember him just flying across the screen with the ex version). Diddy is the only character in the game that has a move that's both visually and mechanically very similar to Deejay's move, so the pick to represent Deejay as a side b spamming Diddy is a very accurate reference to how Deejay was in his games (or at least way more accurate then just using a character that kicks).
Of course change the spirit since it's clearly a problem that shouldn't have been made, but making the argument that the reference is weak in the first place is very ignorant as well to the source material.