AND I STILL THINK IT INDICATES SOME KIND OF BRAIN DAMAGE.
This is definitely not as common as it used to be. Indeed, all lowercase email is much more common these days. But, to my amazement, there are obviously still lots of people in the world who think it’s completely fine and normal to write entire messages in all-caps. While there’s no question that all-caps are strongly associated with ranting cranks, the example that inspired this post was banal: just a person asking a boring question, no emotional content. Just writing an ordinary email in all-caps. As one does. If one is 100% oblivious to written communication norms and so utterly alienated from technology that they don’t understand shift and and caps-lock.
I assume these people hang out with the people who put their entire message in the subject line of an email.