I would de-emphasize the formatted preview, locate it further from the input field and use smaller font for instance. Computer input was never intended to have

I would de-emphasize the formatted preview, locate it further from the input field and use smaller font for instance. Computer input was never intended to have commas. Recent Microsoft Calculator versions that display (and copy/paste!) the commas are a ridiculous failure compared to the original approach. The best fonts are those where there can no confusion between 1, I, & l or O, o, & 0. If you make it big enough for someone with poor vision to be able to see without their glasses, there will be fewer mistakes too. Also for consistency make all big numbers throughout your site text comma-free to serve as something of an example.