In an attempt to salvage the original subject of this thread for Kiwi:

I think there is a true difference between a single quote and an apostrophe. The apostrophe is just the name for the mark in I'm. (It's also talking to an inanimate object, but we won't get into that usage.) The single quote is the name for the marks used for a quote within a quote. The two uses have probably just become confused now because they are the same key on the keyboard.