That's the thing :)
Always dot or comma would mean decimal point - so in your example:
1,000 - means 1
1.000 - means 1
1,000.25 - would generate error (red backgrund of input)
I think it's a matter of being used to way of typing. I never saw someone actually typing both comma and dot in one number through web input fields - other thing when it comes to writing numbers on paper.
But I saw hundreds of times that someone was typing '.' or ',' having in mind decimal point and being angry that system wouldn't let him right one or another to pass the verification.Maybe that's only here in Poland, but I'm pretty shure in GB or USA it's pretty the same especially in banks.
That's why it could be only a local property.
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