Naruto Shippuuden Episode 167

[UChessmaster]

and what evidence do *they* have that they are able to say for example "each character can only use one ability" for example?

How about this? my common sense tells they can only use one ability since so far, they have only use oned ability this battle. There goes one brain cell.

though we've seen 6 different jutsus from the main-pain-body already
even the first summoner pain did use the Kage-bushin Jutsu and this tree trunk-switch thingy-jutsu

Main body Pain =/= dead Pains

Kage bunshin? as already told, Kage bunshin is a basic technique that shouldn`t be counted just like water walking and whatnot, i have no idea what trunk-switch thingy-jutsu is so, ok.

Next we`ll be arguing, talking and moving is an "ability".