After the implementation of the spaces to separate thousands with {{formatnum:}}, sortable tables do not work well with them.
You can test an example in http://es.wikipedia.org/wiki/Usuario:Invadinado/testing-tables
Thanks in advance.
Version: 1.21.x
Severity: major
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=43165