[bee_rider]

I'm surprised at the thank you gesture. The intended use of warning lights is to... warn people, right? I've always understood them to mean "something weird has happened, and so I may do something unpredictable." I can't see how that could have morphed to "thank you."

[Jolter]

Pretty sure the intended use is when stationary, to warn that you have broken down and are positioned badly.

At least, that used to be the only time it was legal to use them here (Sweden). They recently added a rule that it’s legal to use warning lights while being towed, too. Either way, it’s certainly a traffic offense to use them while driving.