Even aside from the voice line, it's gotta be Axel because he was the one leading the charge on the Supreme King's castle in Dark World. Calling him a "fan favourite" is probably just Konami playing hype man unnecessarily.
Well, there is this guy roaming YGO Youtube channels who has become quite famous for asking non-stop for Konami to release more Volcanic support. Maybe they are referring to him?
Anoymous
Dave