Fucking mirrors, how do they work?

I've sometimes encountered arguments or actions that I was inclined to describe as the epitome of human stupidity, but not even in my nightmares did I imagine something like the comments brought to my attention by The Amazing Atheist on his Youtube channel.

Forget magnets and the rappers everybody made fun of for not getting how they work. There are people out there who can't grasp the concept that a mirror inverts images -- i.e., it mirrors them. Let me repeat that: there are grown up people, and apparently of an IQ high enough to enable them to use a computer, who don't fucking understand how a mirror works. One of the objects that's been with us for longer than almost anything else, except maybe knives and the wheel!

What's the story? A Facebook page called Inspirational Transformations posted a classic before-and-after picture of a guy. This one:

Congrats to him, whoever he is, for his "transformation"! I can understand that some people show a certain degree of skepticism with regard to it -- after all, the internet and the media is chock full of fake transforms, most for advertising this and that product.

What I cant't understand is how the hell someone older that 3, and who has an arguably working brain inside their skull instead of some nondescript rotten mush can look at the image on the right and not see that it's a fucking "selfie" taken in front of the fucking bathroom mirror -- or, if they recognize this wonderful and never-seen-before object, not realize that the image is fucking flipped sideways because... well, that's how mirrors work.

My understanding, however, is apparently very limited, because there are people who simply don't get the concept of a mirror, don't recognize one and have no clue what the fuck it does. And if there were only 2 or 3 such comments, I'd write those commenters off as distracted or trolling or being drunk or whatever. But there are over 100 such comments, many of them with more than a dozen "likes". Here they are, in their full-retard glory: