When you hear someone going on about The Rules in English, you should be on your guard, just as when some personage with a clerical collar starts to say, “The Church has always taught. …” You are likely to hear, at best, a misconception, at worst, an outright whopper.
I have tried to establish the usefulness of distinguishing rules from conventions, shibboleths, superstitions, house style, and individual aesthetic preferences.
Take, for example, the eighteenth-century convention of separating subject from verb with a comma. Use it today, and your English teacher will mark it as an error.*
Or, better, take the custom of typing two spaces after a period ending a sentence. It was drilled into generations of students in typing class as a Rule, and it became a firmly established habit. Just try to explain to these people that proportional type in word processing software has made that obsolete, and you get reactions like those of gun owners convinced that black helicopters are in the air, full of jackbooted federal thugs determined to loot their arsenals.**