Is it just me, or spartans in this very early mission (survivalists) have grossly larger night vision than I do? I was shot by a scout from about 25 tiles away and kept getting pounded from all sides not even seeing who does it (I even turned off L lights, even that didn't help). Do they share their targets (as in if one sees a gal, they all do)? Also, is it intentional that we don't have clear indication of who is in darkness and who isn't?
This needs some explaining, as the mechanic at work is *very* unintuitive.
What you experience is the sniper/spotter mechanic. Spartan scouts have the *spotter* poroperty. If they get a glimps of one of your units, they know their location for x amount of turns (usually 2 or 3). No matter if they actually see them, they know the location. You can stand in complete darkness 40 tiles away and they still know the location. They have map hack on your unit.
Next: hitting a spotter enabled unit with a ranged weapon enables the spotter behaviour. You can shoot the spartan scout in the back from 40 tiles away, standing in complete darkness. If the shot connects, the scout sees the unit that made the shot.
Now to do some actual shooting or grenade throwing, the unit must have the *sniper* property. That is a value of for example 33%. This means that unit has a 33% chance to shoot at a target it can not see, but a spotter has knowledge of.
What I'm unsure about is if killing a spotter cancels the knowledge of your unit, but I would assume that is the case. Not sure if unconcious does the same.
As far as I know there is no way in game to find out which units are sniper/spotter. You have to look in the ruleset.
Bottom line, night mission or smoke tactics won't protect you from beeing shot at with sniper/spotter enemies.