Most of these just seem like basic educational issues except this one imo:
Every language has words for yes and no.
I want to see more than like 1 or 2 counterexamples. I'm pretty interested in linguistics on an amateur level. Don't believe I've heard of that one before now.
edit: in retrospect I do think I remember hearing this about Irish and Latin and some older languages. Interesting to know there are so many. I know the theory that language is related to thought patterns is semi-debunked, but I can't help but think that things like this indicate something about the cultures associated with a language.