lidar isn’t able to read the state of traffic lights as far as I know, and I believe lidar based systems detect the location of traffic lights from maps

Lidar cannot identify the state of a traffic light but it can confirm and understand its physical position.

Lidar can't tell a streetlight from a traffic light, so this has to be resolved by vision anyway.

Yeah. But that's not what the OG comment is suggesting. The use of Lidar here would rule out a light resembling a traffic signal by virtue of there being no laser reflection of that object: lidar would complement vision to rule out false positives.

They look different so it should be able to tell them apart if the model has been trained on these shapes. My robot vacuum uses lidar, the maps it makes of my apartment when it cleans are remarkably accurate where you can identify certain objects pretty clearly.

If you overlay the point cloud with the image you're interpreting, it should become apparent that the "yellow light" has no accompanying red or green lamps, no pole holding it, no shroud around it, and is at some distance exceeding the depth limits of your lidar.

I wonder if the concern is that LiDAR looks "ugly" or nerdy on the front of the car. And a bit more aero drag.

Elon can't afford to put LIDAR on cars and sell them to a large audience. It's still too expensive. So instead, he makes excuses for why they don't do it while rolling out objectively worse perception systems.

Lidar can be embedded in the headlights or on the rear view mirror; there is no need for ugly protrusions.

Yeah, then they could never ever ship like every other Lidar company