That's not what I said, there was a full stop, not a comma. I was applying Feynman's idea to writing, if you can't explain something simply in plain English, you really should rewrite it to reach a wider audience.
> I hate seeing advice like "use simple, reduced vocabulary".
Sure, and if articles are written 'normally', for people with English as a second language, that means that they will learn more English words when they encounter new ones.
However "I" is one person, and an author wants to reach the widest audience, with the lowest common denominator. I don't understand much German or French, for example, but an article written in simple German or French is much more accessible to me (the lowest common denominator).
Writing is about reaching all of your audience.