I think the reason it's not discussed is that if there is a bound, it's far outside of human-scale intelligence. Even from my limited human vantage point I can

I think the reason it's not discussed is that if there is a bound, it's far outside of human-scale intelligence. Even from my limited human vantage point I can see virtually limitless ways to improve my own intelligence. Perception improvements, speed improvements, rationality, strategy, physical skills, etc. A being with all the improvements I can specifically think of would be a demigod. Presumably that demigod could build a god, but even if not, a demigod would be a formidable superintelligence.