I've searched pretty extensively and not found a lot of hard info, but here's what I can find:
If a target is destroyed, the firing element gains morale and the target element suffers a loss of morale. This morale gain/loss is doubled if the firing unit is in front-line attack mode. Not a lot of hard numbers on the wiki, surprisingly, but this is an important piece of decision-making information as it implies that you want to have units in front line attack formation to maximize the impact of morale gains (on your own troops) and losses (on enemy troops). Obviously this has to be counterbalanced with the value of high fortification from the defensive stance for units like infantry and statics, especially with Construction units to double that fortification value.
But how much morale is actually lost when a unit is destroyed? It's not made explicit anywhere, but we do have a comment from Steve that
Morale loss is dependent on casualties formation size, so small formations will lose morale quickly. The post also mentioned that mechanics may be modified by playtesting, which suggests that maybe the exact numbers are not posted because Steve was constantly reworking them and never posted the "final" values. Anyways, important information here: large formations are better than small formations from a morale perspective.
Based on this, my
guess as far as hard numbers is that the morale gain/loss is equal to the size of the destroyed element divided by the total formation size, or at least proportionate. This makes perfect sense for morale loss to match the mechanic given above. For morale gain I am not sure if the target formation size is what matters or something else, e.g., the firing formation size.
However as far as decisions to be made I think the basics are obvious: larger formations are better, attacking formations are better, and since morale effects unit stats proportionally and breakthrough chances it makes sense to pull any low-morale unit to the rear echelon rather than risk an enemy breakthrough once it is combat-ineffective. I'm not sure any hard numbers would provide additional insights, particularly anything that isn't already a good or bad idea based on other mechanics (e.g., balance of base class size vs. resilience to fire).
