The 'Suicidal Daimyos' problem?

[Ludens]

I can't say I've ever seen the AI voluntarily withdraw any units myself, in the sense of enabling elements of the reinforcements stack to come into the battle.

He is talking about MTW in which withdrawing (ctrl+W, and not routing: ctrl+R) is a regular feature, unlike STW. In MTW the computer will withdraw depleted units and horse archers with no ammo left. In STW the computer doesn't do that, and many STW players were not aware that there was such a feature.

I think the battle log file records the number of kills for each individual and hence man-by-man honour but it's averaged for the whole unit. Of course, once placed in a bigger unit, they're part of a bigger target and stand a greater chance of dying by missile fire (and small units probably don't attract arrow fire in the first place). I tend to send these units 'back to base' until I've got equal-honour (or better tech) cadres to merge them with as they're of limited use on the battlefield.

Correct: honour is kept track of on individual basis. That's why you can have a 'legendary swordsman' event while none of your units is of high honour. This honour is not lost when you retrain or merge the unit. The men are just as experienced, but there experience is compensated by the inexperience of the other men. Don't worry, they are still there. You can notice this because sometimes the honour of a unit drops when it is taking casualties under missile fire: the experienced men have died.