Yeah, it is objectively bad, because introduces confusion. These systems are supposed to remove ambiguities, not introduce them
If we are being pedantic, technically you should use a space to separate the thousands (e.g. $27 000), as this avoids the ambiguity.
If we ignore that and only focus on comma (,) and period (.) decimal notations, then period for decimals would win out, as the larger majority of the world population use it. So $27,000.00 would be the correct way.
But until the whole world agrees on one, we are stuck with multiple, so you can just rub your two brain cells together and realise that the 3 trailing zeroes probably mean it is in the thousands (along with the rest of the context).
(no shade at the original comment, which was clearly tongue in cheek, idk why it is downvoted lol it was funny)
If we are being pedantic, technically you should use a space to separate the thousands
Exactly. Space doesn’t introduce confusion no matter what sign is used as decimal separator. It’s a such a simple, elegant solution, world would be a better place if people were acrually using it.
technically you should use a space to separate the thousands (e.g. $27 000), as this avoids the ambiguity
But who has time for   in their lives?
(e.g. $27 000)
Ok so they’re winning $27, but I thought it was filmed in America, not Australia. Shouldn’t that be $27 911?
/s, obviously.
But more seriously, yeah a space is brilliant. But you shouldn’t use U+0020, the space you get when you press spacebar. It’s awkwardly wide for this purpose, and more importantly it can break the number over two lines if it happens to line up that way.
The best alternative is U+202F, which is both narrower and non-breaking. Wikipedia claims that the official SI recommended character for thousands separation is U+2009, the thin but breaking space, but I read their source and did not see this supported. It seemed to just say space, without specifying which type of space. There is of course also U+00A0, the no-break normal-width space. Any of these would be better than U+0020.
The problem is them being difficult to type, which is probably why most people tend towards the comma instead. It’s automatically non-breaking and doesn’t have the awkward wideness of U+0020.
Incidentally, SI specifically allows for either the comma or the point to be used as the decimal separator. As long as the thousands separator is a space, this can introduce no ambiguity.