Frustrating...really wanted to try the 1520 until I started to see lots of complaints about the phantom touches. I have the same thing in my Dell Venue 8 Pro and it drives me NUTS. Given that Dell has the same issue, I really wonder if it's a hardware problem in the 1520 since it is now in at least 2 separate manufacturers (of course, Nokia and Dell may use some of the same parts/screen technology).
I've used four different Dell Venue 8 Pros, each one had the accidental doubletap/zoom issue. Which was especially prevalent in the browser. There is however a "User style sheet" fix to disable the double tap to zoom in IE11, leaving only the pinch to zoom activated. I found that to be a solid fix, and made the tablet much more useable. I'm sorry I don't have a direct link, but if you run some searches based on that info I'm sure you'll find it.
As for avoiding the 1520 over a few of the complaints, I say don't. I've had the 1520 since release day and it's easily been one of the best phones I've ever had. I think if Windows Phone was a little more mature, it would easily make owning a small tablet like the Venue redundant. We're seeing definite steps towards that type of maturity in the system as well, so I'm hopeful for the future.
If you're going to purchase a Lumia 1520 through a carrier on contract, most if not all carriers usually offer a 14 day return period. So that way you can demo the phone before being locked into a contract for the foreseeable future.
If you're going to purchase it retail, I highly recommend picking one up at the Microsoft Store. They offer great service and a solid return policy. So either way you should be able to demo the phone risk free.