I have "broken" many a page in my day, if by "broken", someone means "shifted content around on the display level", (and to users with table-based page rendering, this can be a terrifying thing), but the problem there, IMNSHO, is not the newbie user, it's broken CSS programming, and/or a fundamental misunderstanding of content vs. display.
As true as that all may be, I don't think that's what's being talked about. I think people mean when you edit a sentence and end up losing a } somewhere and you end up with the whole article's source code appearing in the infobox or something.
It is an issue, but I'm not sure what the solution is. Complicated templates shouldn't be substed if at all possible, that's an easy one, but more than that, I'm drawing a blank. We need the power of a comprehensive syntax, but the ease of use of a very simply one - I don't think that's possible.