How big is the percentage of people that use itch, but are actually unable to use it in English? If you do sell something, itch is still in the US. Unless direct payment, you even have to pay in $. This might be a rethorical question, but if anyone knows an estimate, I would of course be curious.

And how was the non-english game found? Direct link, or within itch? Because what about tags? Will those be translated as well? Currently they are not. It is not even possible to do so accuratly, as developers use custom tags. 

The tags on Steam are not custom, and they do be translated, because they are finite and translation of game promotion is unfinished without translated tags.

I have doubts that customers are sacrificed. One could also put two descriptions on the same page. Or advertise "on the home market" by website and direct by direct link to itch for purchase - because within itch, how would the game even be found? Would the non English capable customers suddenly use English tags to search for games?

Optionally localized game pages would of course be a cool feature for those devs willing and able to maintain more than one game page. For the rest, automatic translation by client or server will be the solution to go.