I have a lighter at home which everytime I use it, generates little spikes (see picture below) which eventually disappear.
The Spikes are not an effect generated by the camera. I can confirm that since I made the picture.
Essentially this means the flame does not have a nice uniform flame shape, but is interrupted by the spikes.
A different lighter with the same effect, but with the additional feature of beeing able to reduce the gas flow shows, that the spike is independent of the quantity of the gas (right picture).
The height of the spike (distance from the tip of the flame to the tip of the spike) is always the same, thus independent from the quantity of the gas. (In other words: the height from hole that emits the gas to the top the spike is only dependent on the size of the flame)
James did also suggest to light the lighter from an external source, and in this case, no spikes show up.
This implies that its not the gas alone generating this effect, but has rather something to do with the stone.
I don't really know if this is has to do with chemistry at all, or if it has more to do with physics. If thats the case, feel free to redirect me towards the correct SE site.