Ah, but new experts will rise up and embrace the new, friendly Stack Overflow that they have always wanted. And maybe rediscover the same things the bitter, hateful old guard found.
It is NOT 'bad' to use the new keyword. But if you forget it, you will be calling the object constructor as a regular function. If your constructor doesn't check its execution context then it won't notice that 'this' points to different object (ordinarily the global object) instead of the new instance. Therefore your constructor will be adding properties and methods to the global object ...
You should use new when you wish an object to remain in existence until you delete it. If you do not use new then the object will be destroyed when it goes out of scope.
It's all determined by your browser's settings. Using window.open tells the browser to open something new, then the browser opens up what is chosen in its settings - tab or window. In the browsers you tested with, change the settings to open in a new window instead of a tab and you'll see the others' solutions are wrong.