> there’s nothing logarithmic about elo. A 1500 playing a 500 has the same odds as winning as a 2500 playing a 1500, mathematically.

Odds ratios being constant with difference is what you’d expect with a logarithmic scale, with a linear scale you’d expect odds ratios to be constant with the ratio of the ratings.

So, you’ve just explained the way in which elo is logarithmic as your evidence that it is not.