A Deepness of Thought
My nine year old son failed a grammar test at school. He is an A student so this was unusual. In talking with him about it, most of his mistakes were careless. Some mistakes were the using of non-words like "funner". The conversation gave me a spooky feeling of deja vu. It is exactly what I would have done at his age.
At that age, I would have used the non-word "funner" because it seemed logical to me. I would have looked at "more fun" as an arbitrary and confusing. I would have been suborn about this and frustrated my teacher.
Now that I am older, I have a deeper understanding of grammar that I wish my teacher could have explained to me. It is based on a simple and obvious observation: everybody speaks.
We do not all speak that same language but we all speak a language. We do this naturally, no matter our culture or education. Language is a natural capability of the human brain and thus so is, to some extent, grammar. It is located in the temporal lobes. It is not logical the way a computer is or even the way the cerebral cortex is. It is the product of evolution. The brain's rules of grammar are, for the most part, not explicitly known.
The grammar we learn in school is a social convention that attempts to place rules on the brain's grammar. It is full of exceptions because the way we naturally speak is full of exceptions due to the structure of the human brain. The non-word "funner" just naturally sounds a bit awkward compared to "more fun". That could be due to some difficulty in hearing or pronouncing the double "n". Or it could be due to something in the temporal lobe of the brain that science has not yet figured out.
The grammar conventions are important so we can talk to a very large number of people easily and automatically and without the distraction of unexpected grammar. If I had this insight when I was nine years old, I would have understood the value of learning grammar and put more effort into it.
Being aware of your temporal lobe is an opportunity for creativity. You can play with words like "You are funner than the funnest funster." This awareness and cross-connecting of different parts of the brain is the essence of deep thought.