It sounds like he is talking about rasterization which is handled by FreeType.

Kerning is a property of the font, not of the renderer.

I replied to this: http://news.ycombinator.com/item?id=1496177

The problem with Linux typography isn't a lack of fonts, it's bad rendering. I can buy a font from Adobe. I can't buy a better font renderer for Linux.

He couldn't have been talking about individual font properties since he said high quality fonts don't make any difference.

I agree. I think it's remarkable that in taking an overt step to improve Linux typography, they managed to compound their problems by introducing a weak, quirky new default font.