Most spelling mistakes don't mean a thing, but when I read people who write 'of' and 'effect', I assume it's because they don't read a lot. It has nothing to do with intelligence.
People making systematic mistakes is why we don't all speak shakespearian. It's how the DNA of ideas evolves. I'z skateboarden on yur sidewak, levin u behind. Yur Rulez u wasted yur life mastezing our obsoletest. Possible realities are like a fractal wave and evolving languages holographically in the 21st century is more useful then rigidly adhering to rules made by 20th century monkeys thinking 19th century ways. Can u deal with it, grandpa?
The same with 'of'. You picked another word that means something different and put it in there - you didn't just misspell it.
There is nothing wrong with bad spelling - I'm not very good at spelling either. But it's confusing if you substitute words with other words that mean something different, but in your accent sound the same.
The way I speak, those words don't sound the same, and your sentence becomes very confusing. It's only because I've seen this mistake a few times on the internets that I know what is meant.
When I watch british humor, I don't always get it, but I don't expect them to change to be more like me.
Noone can think of a word that evolved in our lifetime already?