On 6 Jul 2016, at 19:31, Rob McBroom wrote:

I wasn’t able to get it to work based on extension either

This is related to Koen Punt’s issue. Settings targeted at file types (globs) don’t work at all in the current release. I hope to push a fix later today.

For example, this will match both plain text and Markdown:
[ text.html.markdown,text.plain ]
This won’t:
[ text.html.markdown, text.plain ]

This is what the parser expects: '[' «string» (';' «string»)* ']'

Here a string can either be quoted or not contain any whitespace.

Though it seems there is no technical reason for this rather strict requirement, so I’ll add a TODO.