But they're both a kilogramme...

I'm gonna punch you in the face the next time I see you

A kilogramme of feathers, because if we consider the miniscule boyancy due to the density of the sack of feathers vs. the dense kilogramme of steel, there must be more than one kilogramme of feathers if we retake the measurement in a vacuum.

Both weigh the same.. I think? I'm not sure what a "kilogramme" is.

neither compare to a kilo of my big juicy ass

They're the same. Here's a better question: what's heavier, a ton of feathers or a ton of gold?

It's a trick question because a tonne of gold is measured in metric tons which are 2,204.62 pounds, while normal tons are 2,000 pounds.

A kilo is a kilo.. No matter of what

Depends whether the feathers are wet or not.