Many Markdown preprocessors, such as the one that Jekyll and GitHub Pages use, have a "smart quotes" feature.

This changes quotes such as

'

to fancier ones such as

’

which unfortunately interferes with KaTeX' ability to render prime symbols correctly.

I propose either ignoring smart quotes and rendering them as ordinary quotes (i.e. if KaTeX encounters ’, it renders it as if it had encountered ') , or introducing an option to do so.