When localizing a display of x/y or lat/lng coordinates, what should I use for a separator? Is it always a comma even in locales that use the comma for the decimal separator?
Regardless of localization factor, accepted formatting standard for GPS lat/long coordinates is: aaa.aaaaaaa, bbb.bbbbbb.
Almost all international search engines will recognize aaa.aaaa, bbb.bbbb as gps coordinates as long as aaa value falls in between -90 and 90 degrees, and bbb value falls in between -180 and 180 degrees.
If you use comma as decimal separator, the search usually breaks.
The best source I found was Wiki article on geographic coordinates for countries that are using decimal comma.
For example, if you go to Italian version of the article, on the left hand side, you'll see links to other languages on the same topic. And you can cross reference it with list of countries that use Decimal Comma.