As with any car, I think you can physically drive it to "absolute empty" - zero gas and zero charge. But there are a lot of risks.
The high voltage battery is limited (10 bars max) and hasarad estimated that under load, a battery bar depletes every 5-10 seconds (100 sec max). You'd also need to drive the car/throttle "lightly" enough that the car's normal hybrid programming wouldn't trigger the ICE to kick on:
https://www.gen3insight.com/forum/2...044-how-drive-my-new-insight-3.html#post19190
With no alternator, it's the high voltage battery that keeps the 12V charged - so depleting the high voltage battery puts all other electrical systems at risk of failure:
https://www.gen3insight.com/forum/7-2019-honda-insight-general-discussion/768-battery-gauges.html
Once you stop the car in "absolute empty" state, there's risk that it may not start-up again since the high voltage battery has discharged too far. (The manual warns that extended periods at low charge shortens battery life, and to run the car at least once every 3 mo to prevent HV battery discharge that will make it 'impossible to start the power system.'):
https://www.gen3insight.com/forum/2...rickle-charge-12v-when-laying-up-insight.html
...and aside from running electrical systems, the 12V battery runs ECU checks at start-up, which would fail and prevent re-start:
https://www.gen3insight.com/forum/1...36-premature-driving-before-system-ready.html
Running to zero gas also puts your fuel pump at risk:
https://www.gen3insight.com/forum/7...ave-you-ever-been-completely-below-slash.html
...and the manual warns that running out of fuel can cause the engine to misfire, damage the catalytic converter, and of course the actual amount of fuel left may differ from the gauge reading (p128).
So I guess in the end, the answer is "it can run to absolute empty gas/battery" but there would be a huge price to pay on the other end. I also think Honda is 'smart' enough to have interlocks and tons of messaging that would alert you and possibly stop the car before irreparable damage.