Regions have specific ways of formatting currencies, these should be reflected in the usage in Workfront. So as a user with German settings I get € 1.234,44 and as a user with US settings I get $1,234.55
The currency format of custom fields has become an issue for us too. We're a global company but report to our Global Finance in U.S. Dollars. When users in other regions enter currency values in custom fields, they often enter using the format they're accustomed to. Following Chris's example above, users mistakenly transpose the use of commas and periods. So when they enter € 1.234,44, it comes across in on our reports $1.23. We have added descriptive text explaining how to enter values, made parts of the text UPPER CASE to call attention to it, provided examples of how-to and how-not-to enter the values, but none of these efforts have paid off yet.
It would be great if when you add a currency field to a custom form, there is an additional setting to indicate what currency you want used and then have built-in validation to ensure the value entered matches the selected currency format.