Wouldn't that require plasma shot to be handled differently than bullets? If it took a conscious effort to leave it in, then it is a feature, even if it was a glitch to begin with. At the same time, cover is not concealment. You might have concealment if you hide behind a table, but if someone fired armor piercing rounds, you only have concealment, not cover. It does make sense that plasma can penetrate things that bullets cannot, provided it's not what we think of as plasma.
The reason you can't see bullets do that is because the glitch is a result of the Aliens being handled EXACTLY like a soldier in everyway. (at least I am assuming so)
So if a soldier would have had a line of sight but the alien wouldn't the alien still can see the unit and still make the attack because a soldier would still be able to make that shot.
It is more of a bug then a glitch... but a bug non-the-less
It gets especially aggrivating if you get shot even though you know that the alien shouldn't be able to see you.
"You might have concealment if you hide behind a table, but if someone fired armor piercing rounds, you only have concealment, not cover. It does make sense that plasma can penetrate things that bullets cannot, provided it's not what we think of as plasma."
Except that doesn't hold up. If an alien takes a shot and the "Cover" is what is hit, it will perfectly block the attack.
The Alien will not shoot through cover, walls, posts, and everything else except when its line of sight (or line of shooting) is blocked.