Testing different configurations I found that the wheel generation chokes and ignores everything after the first Windows-style newline '\r\n'. Meanwhile sdist just copies the string exactly as-is, but inside a Unix-style file, resulting in a PKG-INFO that doesn't break anything but looks weird. And you're also right that this is a bit of pypandoc's fault, because it returns a Windows-style string even if the input was Unix-style, but this is no reason to mix styles or choke.