I think you're being overly harsh on this when it comes to informal communication.
As others pointed out, capitalization is similar to white space, punctuation, and other tools that English has when it comes to informal communication.
Especially online, you can invoke a lot of imagery and thoughts and emotions by simply playing with the rules of English in a live-chat setting. Try to imagine in a chat the following sentence with different stylizations:
"The Customer is always right, so we need to work to correct this"
"thE CUsTomer iS aLWays RIght, So WE neEd To WoRK To cOrrECT thiS"
"the customer is always right, so we need to work to correct this :))))"
The first is quite formal and it's direct; perhaps it could be understood as sarcasm if someone knows you well, but it could also be taken at face value and quite seriously, or it could be taken as a throw-away statement.
The second indicates a mocking tone and maybe even resentment, taking the time to mimic a meme and also to purposefully make the sentence silly looking.
The third introduces the sarcastic smiley (I disagree with the article's interpretation, as I've always seen :))) to more represent desperation or exasperation)
With traditional rules of English, tone is difficult to convey with a single sentence and it's built with the surrounding text as a point of consideration to understand how to interpret a statement; with chat, this is far more difficult to communicate the emotion/intention as chats can be very fast and disconnected, and it's hard to follow the attitude and mood of a person to understand their intended messaging.
You could try to divorce the message from the emotions, which might lead to expediting some discussions, but it also leaves a lot of room for incorrect/wrong interpretations. Even if you divorce yourself from such concerns and try to be above it, your conversation partners might not approach it the same way.
The evolution of chat might be bastardizing the classic rules of English, but it's quite expressive and personally has made many conversations and relationships much easier with fewer misunderstandings.