I might be completely off track, but I believe the answer is
The sentences that lead me to this conclusion are:
I am a ghost
discarnate and sneaky.
Invisible at most.
Catching me is tricky.
A "ghost" as in "can't be perceived when you touch it". Disincarnate because it has "no" mass, hard to catch because studying it has been historically difficult
To cooperate with my persona you need a huge meeting hall
"a person's perceived or evident personality, as that of a well-known official, actor, or celebrity; personal image; public role." from here.In this sense a photon's persona could be the Sun, thus the "huge meeting hall" to cooperate with it
I am very fair
fair meaning bright
and never pick a side
the particle-wave duality
Can't figure out the other hints