[crazygringo]

It seems like it depends a lot on the city/country.

To be clear, I'm talking about rear lights only. The front light is white and always-on so you can see the ground. Plus you can see what's in front of you, so you avoid things, people don't need to avoid you as much.

It's the rear red light that flashes. You yourself don't see the flashing, but it increases visibility so people don't run into you, when you can't see them behind you.

When I'm behind a cyclist with a flashing red rear light, it doesn't bother me. It feels safe. It probably encourages me to keep a little extra distance from them, which is a good thing.