I suspect your problem is related to preference settings for number formats. These used to be based on selecting a region, but were recently changed so you can actually specify formats independently. Try going to Preferences => Number format and choose from the dropdown list an example that you want. See if that fixes the problem.
No, you cannot turn that off. Due to streamlining of Accounts payable/receivable and Supplier/Customer credits input processes, all payments and receipts associated with specific suppliers or customers go through the same protocol. For more information, see the release note: