I think this is because StackIdeas decided to implement currency asap with know issues and requests that would arise....
See here: Marketplace - Currency and sorting options
Mark wrote:

Multiple currencies are not supported yet as of now and it is mainly because of locale issues (placement of the currency sign) . Some currencies require currency to be placed at different locations and some have different decimal format. This is something that we intend to enhance in the future.
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Our database does support multi currencies but we have decided to not allow users to change it mainly because we can foresee people who complain about the placement of currencies as well as the decimal values eventually.
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We'll try to explore these possibilities.

I guess we have to be a little more patient and this issue will be solved

Thanks @supporter.

Regardless, it is a bug. If they don't want you to add a comma, they should prohibit commas from being added to the field, or have a note to the user of the format of the amount and to ommit the comma. It is both a functional and user experience bug.

But, yes I agree, it will improve with time.

James

Hello James,

Good catch. I have added this in our issue tracker.