How much common sense can a designer expect from the user?
Just a minute ago, studio-mate [censored] asked me if I had a calculator around. I said "yes, on the computer". My studio-mate said, "So do I, but it doesn't have a divider". I pointed out the "divide by" button, the one with the slash on it, and asked "what kind of a calculator would it be if it couldn't divide?"
Now it's likely that my studiomate had overlooked the button. That happens, and it doesn't mean that my studio-mate is stupid. But that question "What kind of [app] would it be if it didn't do [y]?" is one that my studio-mate might have asked [my studio-mate's gender in the possessive pronoun]self.
This situation used to happen a lot with The Gimp. Newcomers would come rushing to support forums, torn-out clumps of hair still in their clenched fists, asking "Why doesn't it do straight lines?" and GIMP gurus would patronisingly tell them of the magic key to the left of the Z (on a QWERTY keyboard). There is of course no reason to assume it's obvious that holding down the shift key while using one of the paint tools will result in a straight line. But what should be obvious to users that no one, not even in the world of Open Source software, will be daft enough to release an image creation tool that can't do straight lines.
Or shouldn't it?