I shipped my app in English, watched it do fine in the US and UK, and assumed the rest of the world would catch up once word got around.

It didn't. The install rate in non-English markets was roughly a third of what I saw in English ones, even where I had decent traffic. So I dug into

it, and the answer was embarrassingly simple: people couldn't read my store listing.

Not the description. They can machine-translate that in their head, or the store does it for them. The problem was the screenshots.

Store screenshots are the part nobody localizes