Illustration: Philippe Poirier
The mesmerism token is placed on the staff member as a way to test that they can be mesmerised. For example, Android Greeter and Pod Person cannot have tokens placed on them by the Mesmerist ability, so the mesmerism fails. Because the first part of the sentence fails, you ignore the remainder of the sentence, and do not gain control of the chosen staff ability.
The presence of the token then prevents repeat mesmerism. The token is not removed at the end of the round, it stays in place indefinitely.
Being mesmerised doesn't reset that staff member's ability; if it is only allowed to be used once per round, and it has already used once that round, it's too late.
Previously "Once per Events step: Choose a staff member without a mesmerism token in any park. Add a mesmerism token and move them to your park until the Cleanup step."
This guy's original rule has proven to be quite confusing, and also offered a loophole that wasn't in the spirit of the effect.
The Mesmerist was intended to allow you to take control of a staff member, once, at a critical time, and then return control afterwards.
The approach of moving the mesmerised staff member to your own park put them under your control, and you could technically dismiss them while you controlled them - not thematic for mesmerism.
There was also a question of what happened if the Mesmerist left play after kidnapping a staff member.
So now the reworded version doesn't move the staff member, or give you control to dismiss them. You gain control of the staff member's ability only, and there's no movement between parks, which resolves the question of what happens if the Mesmerist disappears ("there's nothing to undo").