Surely an additional factor is that criticism is actionable, and praise is not? If someone tells me they like my shirt, it feels good, but there's nothing to be done about it. If someone tells me there's a hole in my shirt, then I actually have a new thing I need to deal with. Why would our brains remember comments that are not actionable over ones that are?
I'm not disagreeing with the article, but I suspect this multiplies with the psychological factor.