I'm glad you're mad, but based on this comment and the rest of your comments in this thread it seems that's just your normal operating state. Your argument seems to be that unless someone uses a computer exactly as you do, and has your exact selection of knowledge in their brain, then they're incapable of sharing any knowledge at all. Furthermore, there aren't many Unix/Linux users that operate in a vacuum, and often you'll be using files with extensions that come from other OSes that use extensions; and additionally, file extensions are a useful fast way of knowing exactly what kind of data the file contains. You're a mega idiot who deserves to be constantly seething