Speaking for Dakka, the "rules-lawyering toolbags" are a small ......[brevity].
I will also say that the "firing through another unit" rule is unclear to me, as outlined by others. Are we drawing line across the units heads, and then if that (roughly rectangular) patch obscures 25% of model, it gets cover? If we're just doing the 25% "pixel count" obscuration then that wouldn't be all that different than the normal rule.....and it would have been left better unsaid.
This seems like a holdover from the 5th forest rules --shooting between two trees counted as still shooting through the forest. Speaking of which, that still exists in a way.
There a bunch of rules in the terrain section that a lot of people are nto aware of. One of them being that shooting through a forest always grants a 5+ cover save. So again, we're drawing lines between the trees. This is only for forests, not any area terrain, btw. I also see no special exception for this NOT counting for vehicles, btw. (it's agian not part of area terrain rules, but somethign specific to forests).
Who knew that being behind a hill gives a 4+ save? I didn't, not for the first few months I was playing 6th. BTW, by standard rule, Hills are NOT area terrain and NOT difficult. You could of course have a forest on top of a hill, just understand that is not assumed.
You all know that area terrain can only ever be 5+, right? By default, Ruins are not area terrain, though they are always difficult. A lot of people like to play Ruins as being both ruins and area terrain (I really count myself in that group), but if you're going to ground in ruin, you're getting a +2 to cover off the 5+, or a +1 of the 4+, whichever, you wind up with a 3+ cover save, not a 2+. You'd need stealth or some other special rule for that.
And here's the big one that people get wrong -- The target model gets a cover save if it is obscured from the point of view of ANY model that is firing at it. Note that a model cannot fire at a target if it can't see it. So 30 models firing in the clear? No cover. 29 models firing on a MC and one is stuck behind a tree and can't see it at all? No cover. 29 models can see clear but from the last guy it's 25% obscured behind the corner of a building? 4+ cover save.
Now if you point out that the model is in cover because of that 30th guy, I think a lot of people would think you're a jerk. But it is the rule. And an easy solution is the firer could just choose not to fire that 30th guy.