I've been a technical writer for many years, where anything written has to be precise and exact. I've had to get used to the abominations of language (shudder) that I see in email/text/tweets, but there's no fighting progress. After getting a cell phone and laboriously picking out the letters for a text message, I understood fully the all-lower-case thing. I like Jay Leno's joke about texting when he said maybe someday someone will invent something where you can just SAY the words. Yep, I'm sticking with voice messages.
Bottom line is - old habits die hard, so I continue to try to punctuate and spell correctly, no matter what the medium. Hence my "properly capitalized" user name.