> a moat interrupts the view

No, it doesn't: it's just a ditch. (But it's not very effective as a defensive element if not combined with a wall).

Skimming through the first hundred or so hits on “moat” on images.google.com shows that pretty much every single one does in fact interrupt the view.

So at the very least, keeping a clean view isn’t a fundamental property of moats. But keeping a clean view is the raison d’etre for haha’s. In fact that’s how they get their name.

Moats do in fact provide a very clear view of whatever is on the other side (often a castle or a wall). But of course that's not why they are built, nobody disputes that.

The key here is “uninterrupted” and “clean”. with a well done haha, you can’t tell that anything is there at all. With most moats, you can.