There is no way to tell from the listings page unfortunately. Once you receive the product non-commingled items will have a sticker over the EAN/UPC/Barcode which includes the sellers own SKU, barcode, item condition (New, Used) and item name. If the product doesn't have one of these stickers and the EAN/UPC is uncovered it is most likely commingled.

You can always contact the seller, who has to maintain a 24h response time average to maintain their selling privileges.

As a seller, I would much rather you contacted me before buying. My average response time is 8 minutes and most big sellers I know are <3 hours.

I'm not sure, but I think it's denoted by the "also sold by these 433 sellers" line (or similar) below the price.