Sun has no atmosphere per se nor oxygen yet it still produces "flames".
What "flames" are is either a by-product of photon particles or ionization of dormant (non-reactive) particles when two chemicals/elements react or a single chemical/element reaches different "aggregation state" (be it either violent reaction or "explosions" or a steady "burn" through some sort of "ignition"/"excitation", like gamma/beta/... radiation, nuclear fusion, particle friction,... magnetic fields even)... yada, yada,... (I made this all up BTW
) So "light" or "flames" aren't even close to being "rare" in space. But yeah, B5 used "proper" physical models of space and SGA doesn't. Does that make it any worse is another question? (It does in my eyes
)