Columns still have normal facing, as if they were in the open. Units in line are dispersed inside buildings and gardens while units in column are jammed in the streets. Rule 25.3c creates some odd effects, particularly routing skirmishers that makes squares panic as they run past. That was not intended when the rule was changed. Using this rule a retreating unit passing through a stack only affects units lighter than itself and units of the same weight and with morale equal or lower than the retreater.
Heavier units ignore the whole thing.
If stacks consists of units of different weight use the heaviest one in the stack. When an order to consolidate is accepted the entire cavalry formation must spend an entire turn stationary fulfilling all straggler recovery requirements for the actual consolidation to happen. The disbanded unit are of course counted as destroyed for victory and wreckage purposes. This might be a good idea, and then again not. Frankly I'm not sure.