Commas delimiters appear for all numeric fields in ArcGIS Online by default, though you can specify where to supress the commas (to display the numeric values without the commas). This may sound like it makes sense, but in practical use, we believe the logic should be reversed. Instead of specifying where to supress the commas, commas delimiters should not be applied by default. They should only be shown in cases where commas have been specified in configuation.
It is true, some numeric field containing values like population, scientific measurements, higher elevations, etc require comma delimiater. However, the vast majority of numeric fields in any orgaization's layers are fields such as database keys or identifiers, which should not use the comma delimiter. In our case, we have less than 5 fields requiring commas, while we have well over a 100 instances of numeric fields that we must specificly turn off the commas. This is a lot of work for something that may not sound like a big deal, but you would be surprized by the volume of comments we received from our users to remove the commas.
If others agree that the logic on this is backwards, please support us in asking Esri to make this change.
