Sure, is just that in hardcore the slaves tend to rebel more and some punishment after a beating... well it's a kinda compelling strat
A compelling strategy is one that works, no?
Punishment increases obedience by increasing the slave's fear, if used correctly, but you need to be careful with it. Punishment also impacts the slave's mood, and over time an unhappy slave will lose hope and fall into despair. Punishment effectiveness also depends on the master's skill, and the slave's attributes and traits. There are situations where leaving a slave depressed and miserable can be tactically beneficial, but you'll usually find it much easier to train a slave if you prioritize keeping their mood up, balancing punishments with rewards. Of course, if a slave isn't willing to obey anything, it's difficult to get them to earn merit. But, for most slaves, it doesn't take more than a day or two of effective punishments before you can find something they won't refuse to do. Whether that's a lesson with you, sending them to school, hiring a tutor, having them cook or clean the house (not as a lesson), do gymnastics, etc. Also, keep an eye on the slave's empathy attribute. A slave with high empathy is more prone to despair (as explained in the tutorial and in the help text displayed when you click on the slave's empathy attribute).
It was a loop in the recovery logic. When the slave reached D- endurance and woke up, it was dropping her back to F- so she immediately fainted again.
Supplements help, as you correctly thought.
In terms of recovery time, sleeping in bed is no different than sleeping in a bedroll if the slave is unconscious. Sleeping on the floor (without even a bedroll) would slow recovery a bit, as would sleeping in a prison cell (not a surprise, right?).
