Sorry for dragging it on, but I'm still a bit sketchy on some of em-
As the first 470uF is a bypass cap, it could technically be placed somewhere else, right?
Can you elaborate on what the 100uF does? What precisely is this "feedback"?
Out of pin 5, am I right in thinking no DC current can pass through the 470uF cap to the speaker?
Feedback is output that gets into the input. If it is positive feedback then oscillation will occur. If it is negative feedback then amplification is reduced.
Out of pin 5, am I right in thinking no DC current can pass through the 470uF cap to the speaker?
Correct. A capacitor passes AC but blocks DC.
The output of the LM386 is about 4.5VDC when the circuit has a 9V battery. If the capacitor wasn't there then the 4.5V across the 8 ohm speaker would cause a DC current of 4.5V/8= 563mA which would quickly kill a 9V battery and cause the speaker's cone to be offset.