Defining characteristics = Two horizontal lines?

Ok.

I mean, they're both dealing with the same design constraint: fit the antenna into the shell to take up less room in the device. You can trace both this 3-part-back panel back to the iPhone 4, along with the entire concept of putting the antenna into the shell.

I don't care either way. I liked my X8 when I had it, but I won't buy a product form a company that is clearly copying someone else's design. HTC is only hurting themselves by not trying to stand out anymore. And on the other side of the fence, if Apple sees this as a real problem, they'll be forced to make their designs less easy to copy (integrate unique patents or manufacturing processes into their design).