When setting lang:es in the header, the . decimal separator is not rendered at all (it's supposed to be transformed to a comma). French still renders the decimal separator though.

pandoc version:
pandoc.exe 2.11.1
Compiled with pandoc-types 1.22, texmath 0.12.0.3, skylighting 0.10.0.3,
citeproc 0.1.0.3, ipynb 0.1