Liquid Damaged Stamps

Are stamps with water damage or coffee stains still usabale for postage?

At your own risk?

Roll the dice if a postal employee will consider them damaged, mutilated or defaced.
Don

Take your items to the post office and have them hand cancelled. Done deal.

I realize that a cancelling or defacing machine probably won't be able to read a damaged stamp such as the one in the enclosed photo. However, if a sheet with stamps in that condition were placed on a box to be hand cancelled at a post office, would a USPS employee deem them not valid? I ask because I see listings for damaged stamps on auction sites and they sell, so I'm wondering if people use damaged stamps when mailing at a post office?

The following is a customer support ruling on torn postage stamps, which doesn't apply to the photo I posted in the message above, but it's interesting that the ruling uses the word common sense. I wonder if common sense would apply to the stamps in the photo above regarding defacing?

https://pe.usps.com/text/csr/PS-281.htm