I appreciate the concern (really), but it's been working for >20 years now without any fires, and as I gradually replace the incandescent and halogen bulbs with much lower wattage LEDs, the load and risk reduces accordingly.
The house was dual wired with domestic 3-core 240 VAC 10amp cable - live, neutral and earth. Cable leading to light switches and sockets was powered from the DC bus, i.e. directly from the batteries, and only used 2 of the 3 wires, for positive and negative. Cables leading to conventional GPO sockets was powered by the AC bus, i.e. from the inverter, and was wired up according to code - live, neutral and earth.
There are many more DC cable runs than you would otherwise expect, because each run was designed to carry only up to 10 amps, which would have been no more than 4 x 60-watt bulbs (24 VDC nominal). I was able to replace some of the conventional bulbs with lower-wattage-for-the-same-light-output halogen items, and reduce the amperage load further, and now that drop-in LEDs are available, there's bugger-all load on some of the circuits.
In practice, the DC circuit voltage is lowest (24 to 24.2 volts) when there's little load on the lighting circuit (about 10pm to 7am), and highest in the middle of the day, up to 30 volts until the batteries reach float, where they stay at 27.4 volts until late afternoon when the sun goes down, dropping rapidly to about 25 volts, then slowly over the evening falling to about 24.2. So the higher practical voltages of the circuit mean even lower amperage for a given load in watts, and this also compensates somewhat for the voltage drop at the far end of some of the circuits.