If one person teaches my agent a rule, does it apply to everyone?

Not automatically. Your agent remembers who gave each instruction and the context it applies to, so one person's preference (for example a US tax assumption) doesn't silently become everyone's.

Best practice: when you give a rule, say whether it's for a specific project or universal. Have universal rules approved by the agent's manager. If you ever see a rule bleed across people, tell us and we'll correct it.