Yes, it's signed. That means the values don't actually represent 0 to 65,536. The values represent -32768 to +32767. This represents the waveform on both the positive side as well as the negative side the waveform (mid point representing 0 volts). When the 16-bit word is read, DAC knows to output 0 volts DC when the 16-bit data word represents the mid point. However, it is still 65,536 different actual points of voltage. It is not 8 bits positive and 8 bits negative. An 8 bit word would only represent about 256 different steps and that is not nearly enough for audio.
I also never said it was not a "A/C" waveform (A/C meaning alternating current). I only said it was not a true "analog waveform". As opposed to a digital waveform, which is usually interpreted to be "square stepped" or "on/off" in most cases.
I'm going to politely state the above as known facts for everyone who doesn't know and not respond from a post that I see only as a troll intending to start a flame war.