Why can't vehicles and infantry make smoke?

Vehicle based smoke dispensers would be an unnecessary game complication and is already factored into the Point Fire Table. Infantry units have a very limited ability to generate very small amounts of smoke, as with the vehicles, this is already factored into the game's tables. Neither causes enough of a stir to warrant marking the map with smoke.

What's the point of "Persistent Chem" markers in the Modern Expansion?

They attack any unit which enters their hex after they land. Nonpersistent chem only attacks when it lands, persistent does this also, but then hangs around to make life tough for a while.

What's the advantage of being in a Hasty Defense? You don't have dug-in status as Prepared Defenses, so what's the point?

Hasty defenses are quicker to establish than prepared ones and the units won't have to "run away" like they would if they were "without orders."

Since TRPs are chosen before play, must they be observable by friendly units at the beginning?

No. TRP's are free to be established anywhere and do not have to be observed.

What is a "section sized unit?

A section is a two step unit usually marked with a two dot size in its unit symbol. About 12-15 men.

Why does move mode units in a City/Village hex get a +1 terrain modifier on the Area Fire Table? Shouldn't this be a -1?

+1 is correct. Move mode units are assumed to be in the street, moving. They may be taking advantage of the walls, etc., but they still must negotiate corners and cross in front of cross-streets, which are always deadly traps. They are exposed more than the usual group so they get a +1.

Does Mounted Infantry provide the -2 Die roll modifier against AT Rolls?

In the standard TCS yes, in the Modern Expansion, no when speaking of enclosed MICV's.

Can ICM (no effect on vehicles with defense of 2 or more) still roll on the Artillery/Mortars vs. Point Target Table?

No. Once the bomblets are dispered, there is no large round left that might destroy a vehicle.

Do Pop-ups in Suppressive Fire need an LOS or are they exempt as in overwatchfire?

These pop ups are also freed from regular LOS. An LOS from 100 meters is needed to fire, but none before the pop-up.

How are both type targets engaged by Chem attack?

They are hit as area targets and as point targets.

When using AA fires in the Suppressive Fire Phase, do all get to shoot? Or, do you alternate on a firer by firer basis?

AA fires are like AT Rolls in that a firer can engage any number of targets. The problem is that they are not restricted by range as much and are less controlled because of it. As a literal interpretation, they all fire on each target in succession. The problem is that the original AA rules were written with air sorties in mind, and not on map helicopters. As a house rule, I would suggest adopting the firer by firer alternation when speaking of AA fires, allowing multiple AA attacks on a single target and of allowing the horizon to light up on a single target at a time.

Some AA units require LOS but not visibility. Can these units fire through smoke?

Yes. Smoke in this case is considered a "visibility hinderance" and nothing more. AA units of this type ignore smoke. Also, AA units which do require visibility may fire out of a smoke hex, but not through one.