Thanks for bringing this to our attention! I was able to reproduce your issue using the preview feature in Azure portal. You can also choose Edit and this will display the CSV file with commas.
I am reporting this issue to our internal Storage team for review and fix. As a workaround you can use Azure Storage Explorer. I confirmed the preview feature works as expected.
Hope this helps. Apologies for the issue, I will provide an update if I confirm this issue is resolved.
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