"The coach never taught me such passive boxing." Actually, he did, by virtue of not correcting you, which is what coaches are meant to do. I hate Kamogawa and Ippo's braindead loyalty to him SO MUCH.
This chapter gives me a theory, though. He kept fighting brainlessly for years. Now, of course everyone else should've told him that. But, why did he never notice himself? Clearly, because all the concussions and blunt trauma. But the brain doesn't just heal from that. Yet Ippo's brain seems to have done just that. How? The answer is clear: Ippo's brain is actually a symbiotic slime mold, capable of slowly pulling itself back together over time. That neatly explains his stupidity, resilience, and recovery.