General Liederkranz

If you give the team a face command at the end of the movement orders then that will cancel the cover arc. That's how it works way back to v1. Now if you are not adding a face command then that would be a bug. If you need them to face a certain direction then give them an arc in the direction you want them to face an then after they are settled switch back to a circular cover arc and all will be well.
If you have an instance where the orders did not include a face command (or a target command) and the cover arch was dropped then save it and share and someone will get it logged and fixed. I do this frequently when playing and have not seen a problem. I will watch carefully over the next few days just to be sure.

This problem still exists. Beyond ~150m you get single shots from Brens and Bars. In fact you get 0 practical firepower from an American or British rifle section beyond 200m, unless you manually area fire, since then everybody, except the Bren/Bar does not fire at all. An exception is if the targets are running upright, then the rifles might fire a couple shots. I have a test range setup, and the total fire output from a British rifle squad, without manual target order, against an enemy squad not moving, is around 3-10 rounds per minute, only fired from the Bren/Bar.

I assume it's generalised - I don't know how the values are derived, but the intention is surely worst-case (since the point of it is "how not to get your own men killed")

From vague memory of a discussion here, I believe the way CM models HE shrapnel is an explosive effect, followed by a number of randomly drawn straight-line traces, from the impact point. That inevitably will mean that in some scenarios it'll be better to be prone (they'll pass overhead in the y-axis), and in some scenarios it'll be better to be standing (if the path is grazing the ground, then being prone will create more x-axis targets to hit.

What does not seem to be modeled is the deadly effect of "blast" pressure even if one is not hit by shrapnel.

Sorry to have misled you! I see that they do in CMFB. I've been playing CMFI a lot lately, where they don't, and wrote without realizing they now had radios in CMFB.

Yes there’s been another thread on this, or maybe for company HQs. In-game there’s a little blue box that says “HQ” in white in the upper left of the unit info area. Clicking it toggles between this view, in which you can see the HQ’s subunits, and the ordinary view in which you can see all the members. Seems like it’s permanenrly stuck toggled on in the adversary AAR view?

It seems weird if the mortars don't stay in C2 based on proximity to their company commander (voice/close visual). But the rules for calling indirect fire are different from the rules for C2--the mortars need a communications link with the platoon HQs calling the fire, not just with the company HQ. The problem here might be that armored infantry platoon HQs, unlike their regular counterparts, don't have radios. So the missing link wouldn't be between the mortars and the company HQ, but between the platoon HQs and the Company. Just a guess.

Were you able to issue a separate Dismount command using that button? Or just a movement order for the riders (which, in v4, would've automatically said "Dismount" over the waypoint)? In my experience you can't issue a separate Dismount command (the button is unclickable) from a vehicle that still has movement waypoints plotted, even if the vehicle is paused. Without that, the Dismount that's "included" in an ordinary movement order for the riders won't take effect unless the vehicle is stopped with no more waypoints plotted.
In this situation I think you would have to first cancel the tank's orders, then issue a separate Dismount command for the riders, plus their own movement orders, and then plot new orders (with a Pause) for the tank.

A squad or team can use a buddy-aided radio for C2; I’ve tried this and it works. As long as their immediate HQ still has a radio of its own of course. 

Or have I just not noticed them before? I'm playing the scenario "Eye of the Needle" in v4.0 and two things have happened that struck me as odd. 
1) Su-76Ms that have a small amount of HE and a lot of AP remaining have repeatedly used AP against individual Germans manning heavy weapons. I thought this was great since it took out the enemy and didn't waste precious HE, but it's not something I recall seeing before. It seems like a very clever AI ammo choice.
2) A Soviet Rifle Platoon that has lost its commander (included in 1st Squad) is somehow maintaining C2 over its squads. I thought in the past I've specifically noticed that Soviet Rifle Platoons that have the commander in 1st Squad a) don't have XOs and b ) therefore lose C2 completely when the commander is killed. They don't have any higher HQs within voice/close visual range (50m) that could be keeping them in C2.

One way to get a sense of relative elevation is to install a gridded terrain mod. I tried one and didn't like the look of it, but it does help see small hills and dips.

http://cmmodsiii.greenasjade.net/?p=2295

In my experience this is usually (though not always) due to infantry posture--as I understand it, the Target tool will show you LOS from that unit *from its current height* as if it were at that position. But infantry heights change during play based on their posture. Often, especially early in the game, you'll be measuring from an infantry unit that is safely behind the lines and standing or kneeling. But if you crawl (Slow) them into that position, they'll be lower down, and possibly able to see. It can happen in reverse if your unit is currently down on their bellies but you expect them to be kneeling when they get there--e.g. if they're going to end up behind a wall. 
I agree about drawing multiple fake waypoints to check LOS. Getting down to camera level 1 and walking the battlefield before the game to see what you can see from various spots can also be helpful (keeping in mind that this doesn't get you as low down as infantry; I think it approximates an average vehicle height?)

There are many threads on artillery targeting but it's worth mentioning, if you haven't seen it already @JPFisher55, you can target places out of view if you have a TRP there (or within 50m), or if you're doing it before the game starts. You can even target a spot out of sight, then put a 15-minute delay on it. If you find after the game starts that you don't want to hit that spot, you can cancel the fire mission.

In my experience this is usually (though not always) due to infantry posture--as I understand it, the Target tool will show you LOS from that unit *from its current height* as if it were at that position. But infantry heights change during play based on their posture. Often, especially early in the game, you'll be measuring from an infantry unit that is safely behind the lines and standing or kneeling. But if you crawl (Slow) them into that position, they'll be lower down, and possibly able to see. It can happen in reverse if your unit is currently down on their bellies but you expect them to be kneeling when they get there--e.g. if they're going to end up behind a wall. 
I agree about drawing multiple fake waypoints to check LOS. Getting down to camera level 1 and walking the battlefield before the game to see what you can see from various spots can also be helpful (keeping in mind that this doesn't get you as low down as infantry; I think it approximates an average vehicle height?)

There are many threads on artillery targeting but it's worth mentioning, if you haven't seen it already @JPFisher55, you can target places out of view if you have a TRP there (or within 50m), or if you're doing it before the game starts. You can even target a spot out of sight, then put a 15-minute delay on it. If you find after the game starts that you don't want to hit that spot, you can cancel the fire mission.

I'm wondering if this is a bug or intended behavior I've just never noticed before. In the CMFI scenario "Fight at Vallebruca," the Americans start with one on-map 60mm mortar team. The team is carrying 32 rounds, but the mortar shows 64 available. No one else on the map is carrying those 32 rounds. I'm able to fire all of them. Then, a few minutes later, the Americans get reinforcements, including another 60mm mortar team. And the extra rounds that the first team previous used, are already deducted from the number of shells the second team is carrying. It seems that they were sharing their ammo, even though they were not on the map yet. Is this normal?
(there are two set-up zones for the Americans on that map, and I found that the original mortar team gets the extra ammo only if they're deployed in one of them, where the second mortar team later comes it. So again it seems like the game is assuming the second team is hanging out just off the map, sharing its ammo)

To make sure I wasn't remembering wrong, I just tested this in CMFI by running an HQ into MG fire. When the Radio Operator went down, the radio disappeared from the unit's equipment panel. But when the CO Buddy Aided him, the radio reappeared in the UI equipment panel and the unit went back into radio C2. However, the CO didn't change graphically--the radio backpack didn't appear on him.