Here’s my take on humanity and stains:
The higher your humanity is, the more guilt you will feel due to negative actions. Stains represent this guilt.
So if you have humanity of 9 then you can only get a single stain before becoming overwhelmed with guilt. This triggers the remorse test roll. If you succeed in the test, then you forgive your actions THIS TIME and remove all stains. If you fail the roll, then you lose one point in humanity and remove all stains.
At 8 humanity you can get two stains before the remorse test is triggered. Same rolls and results apply.
Humanity 7 you can collect 3 stains, and so on and so forth.
This is how I employ forced remorse tests.
Other options: allow players to roll remorse as soon as they get stains, or roll remorse at the end of the night.
For voluntary remorse rolls, the player gets to roll as many dice as they have unmarked blanks in the humanity tracker. So a humanity 7 vampire with 1 stain, would roll 2 dice trying to get a single success. A humanity 3 vampire with 1 stain would roll 6 dice trying to get a single success.
Thus, a lower humanity rating means you can do more deplorable acts before actually feeling bad about it, or before it actually reduces your humanity further.
There’s a chart for humanity on the story tellers screen that breaks down the bonuses and banes by humanity rating as well.
Personally, I do not give stains for feeding alone. If vampires drain a vessel completely, killing them, then they get a stain for that. Not for feeding. Then how do they dispose of the body? If they bury the body, that’s a respectable action, no additional stains. But if they throw the body in the river, in a mine shaft or something along those lines… That’s desecration of a corpse, so they get additional stains depending on their actions.
Basically speaking, anything a character blatantly does that actually makes them seem monstrous, can result in a stain. ie…breaking into an orphanage at midnight just to scare all the kids would get you a stain at my table.
I hope this helps answer your question.