I think i was expecting us to have multiple such styles, but this is
just not happening, so it seems odd to just have that one extra
directory with only one file in it.

Having the file named "mdl" something will also make it easier to
understand what it's about.

more precise

This was the next file in the list, and a good one to test because I
didn't write it. I removed some warnings that seemed ludicrous but
otherwise cleaned up the file to match the others.

We had to create a style because we can't just use a `.mdlrc` if we
want to customize some rule settings (e.g. for rule MD026).