It’s probably wrong to say it’s a bug with the API. The old spotlite interface which these used accepted just about anything, so you could almost certainly post a spot with a frequency of “FORTY ONE POINT TWO THREE METRES” if you so desired. The API enforced valid frequencies, and has published documentation that states input is decimals using a ‘.’ as decimal separator, and SW3 as a client enforces this as well.
The only place that can be locale aware is at the client side, so really SOTA Spotter or SOTA Goat should do the conversion to ‘.’ before posting to the API.
Having said that, I’ll patch the API anyway to alter any commas to ‘.’ since it’s easy enough to do, but it will fall back on the client to still ensure that the frequency submitted is valid, ie, ‘1,296.100’ as a frequency will necessarily have to fail despite that being a valid locale-specific form of a 23cm frequency (which the API would have parsed correctly until the frequency changes a few days back to disable kHz spotting).