Reasons of why the signs of the capacitor of the diagram is correct?
Intuitively if you start with all the capacitors zero voltage and apply current to Node 1 relative to Node 2 (call that ground) until the voltage at Node 1 is 5V then the polarities will be as shown because C4 &gt; C3 and C1 = C2.
That's because more voltage will be dropped across the smaller capacitance.
The presence of C5 does not change the polarity but it will reduce the difference.