Finally, what may be the least complicated explanation is the smell that people are experiencing during the experiment.
The smell is likely coming from the fumes from the butane in the lighter. If you've ever used a lighter before, you can smell the chemicals.
As a meteorologist, the idea of modified snow is quite silly.
This wasn't a government "test" to see how people would react to snow, nor were the clouds "seeded" to produce snow in places that don't normally get it.
Despite its pure, white color, snow is anything from pure, especially because of pollution. But even with the trace chemicals snow absorbs as it falls through the atmosphere, it isn't supernatural. http://www.wdbj7.com/weather/why-this-weeks-snow-wasnt-normal/-/20128370/24210298/-/ubbcty/-/index.html
We get the same petroleum like smell using a match too.
I figured the lighter would give off something BUT I don't get the same smell when I use it on ice out of the frig. Of course Ice and snow are very different structure wise. maybe being denser and as such ice melted by lighter gives off a good bit of water the water absorbs the smell of the lighter and or match and it goes down the drain in the sink.
Where as the black stuff on the snow stays there and keeps stinking..