At first I was thinking that, yes, Syndesia and humans are 'Neutral' but they are, at least nominally, more good than evil, in that they have more in common with good than evil as a rule.
However, adding in the post by @Rife about neutral alignment, there is a point to be made for changing Syndesia and what it means to be 'Neutral'
This would have to also take into account the discrepancy with loot drops for different alignments.
If Tartaros is evil, and any good players there have only a short stay, debuffs(?) and the entire population after their heads, with Arboreus being the opposite, then why not make Syndesia truly, if not neutral, then at least equal?
Give good players in Tartaros the same problems as evil players in Arboreus, with full loot drop if you like, but equal if opposite, and give good and evil players the same legal penalties on Syndesia.
Make it so that in the same way that good players can hunt down and imprison evil players, evil players can do the same to good players. Since there will be evil aligned cities and regions anyway, then this way neither alignment can complain about unfair treatment.
Neutral players on the other hand, should have both greater and less protection; on the one hand, while good players in evil zones will likely be attacked on site, and vice versa, though every player will react differently, then Neutral players in either good or evil zones could be viewed as untouchable, being attached to neither side; enemies, because they are not allies; spies, traders, whatever the situation calls for.
Neutral players should be able to be attacked by any, because they refuse the security of either side, but potentially be attacked by neither for the same reason. They should be able to attack any (though not steal I would say, crimes aside from murder should be kept solely for evil alignment, only because there is no other way to protect against theft than to have the one side incapable and the other side visible as potential criminals, if there could be another way to register criminal activity that would be good, but as it is...) but karma would still be affected normally (there is a point where negative karma forces alignment change to evil isn't there?)