Okay, I didn't expect what I considered to be a gameplay and a logical issues to raise to a game-philosophy discussion, but thanks Qwerty for defending this point of view with much more verve and patience than I could ever produce in an english debate haha
There is a very important point I was not aware of: encourage, threaten and put in place have a reduced effect with time. It should be clearer, because it's absolutely not instinctive. If you use it during a whole week you will obtain exactly the same sentence. I saw it change in the rare case where I was using it during a decade, but I was absolutely not sure it was because of the repetition of the action...
I would like to add that for a "end game" perk, put in place is quite easy to use when starting a "normal" game.
Because if you can drop the level of spoil during the day, no amount of spoil that is gained overnight will raise it again by more than one level (because overflow points are reset when level changes).
True: I forgot about it, but you can't spoil very fast a slave because of this feature.
...finally... everything has been said, and well said: I just had an instinctive scepticism about a weird situation.
We can talk for ever about it, but, it was a pretty clear case for me:
"With a stern voice you explain to your slave that your good attitude towards her is not infinite."
The slaver punish her every day. She sleeps on the ground. She eats bad food. She has been forced into slavery.
As a slaver who starts training you NEVER have a good attitude towards her (expect when you over-reward her, etc.)
Does not establishing rules beyond "obey me", "sleep on this harsh bedroll", and "be a good slave" can really spoil her?
For me there is a total gap between the nightmare of the early training, with his load of punishments, and you telling the slave "don't act like a spoiled princess": I think in other circumstances she would have just laugh in your face^^ "you just give me to the crowd, but you think its necessary to tell me that "your good attitude towards me is not infinite." ? haha!"
Oooon the other hand... when she starts to become obedient: you punish her less and less. That's where it should be needed to establish rules, and to be REALLY aware to not spoil her.
I already said it, but currently not spoiling a slave is only ticking the same boxes for every slaves. It's not about being easy or difficult: it's just boring. I do not want having to tell to each slave "don't masturbate", to avoid them to be spoiled. Anyway they have other things in mind than thinking about this, I guess...
Finally, increasing the impact of fear could be a first solution. Make "put in place" a more powerful but one-shot action could also be a solution. Slowly increasing the needed rules could be another solutions which I pretty like (in parallel with taming or awareness, eg.)