I don't know of a compiler that forces you to use the newest version of the standard, which is why I've always kind of thought "don't break old code" was treate

I don't know of a compiler that forces you to use the newest version of the standard, which is why I've always kind of thought "don't break old code" was treated too much like dogma. So from that perspective, a non issue. However, there is a problem that has nothing to do with old code: they increased the number of situations that constitute undefined behavior, with no public discussion and no justification. It's frankly dangerous behavior.