By writing one letter at a time, you're not utilizing your "full communication" power. In fact you're using just 1/26 of the power of the alphabet, that comes at 3.84%. So, instead, write with a superposition of all letters at once to utilize 100% of the power of the alphabet, using 100% of the brain.
Presumably that would mean all 26 letters printed on top of each other.
There's a silly old factoid about how "you only use 10 percent of your brain," which psychics and other woo-peddlers use to sell their personal solutions for opening up the potential of the unused 90%. Of course the idea that you can think better if you use 100% of your brain at once is as silly as the idea that you can communicate better if you use 100% of the alphabet at once, which was Visarga's point.
That's not what the article is talking about specifically, but the bit about "using your full brain" does raise unfortunate associations.
The logic that we are using "only a small part" of our brain is caused by the sparse activations. When perceiving something, we need to encode the raw sense data. When encoded, only a small part of the brain is necessary to represent it, thus the misconception that we are only "using" that part. In fact we are using all of it, even the inactive parts. By analogy, when I am writing, I am only using one letter at a time. This does not imply that I am only using 4% of the power of the alphabet, just that it works by sparse combinations. Thus there is no basis to thinking that we could improve if only we could use 100% of our neurons at once.
