Yeah, that caught me off guard too. The description needs a bit of rework.

Nope, it means it is the delimiter between the latitute and the longitude. The description is technically correct since a comma can and will be in the string.

The description says

"Coordinates can only contain digits, or one of the following symbols (including space after comma) -, ."

So I thought the comma could also occur within a coordinate.

Commas are used as delimiters in this scenario, therefore your example of "0, 1,2" treats it like [0, 1, 2] instead of [1, 1.2].

We are using full stops "." as decimal point markers, not commas. So "0, 1.2" is valid but "0, 1,2" is not because "0, 1,2" has three values instead of 2 (lat and long)

Why is "0, 1,2" invalid?
Latitude is between -90 and 90 -> 0 = valid
Longitude is between -180 and 180 and valid symbols are , and . -> 1,2 = valid

Or am i getting anything wrong?