There is no night capping, only population imbalance. The only way to stop population imbalance, is to limit the lead population to 10% over the least population.
Many of the people complaining of population imbalance at "night" obviously don't play at this time. Most of the time all factions are 2-3 bar the difference is who is organised and who has the most resources.
If AD has Ash and BRK it is difficult to get them back with a low population for example. If DC has Chalman and Roe same problem. The faction with the most real estate just moves to the fight.
Playing at low population time is different, some factions seem to get it right more often.