Also, donating will help with persuading people to be more altruistic in general. In psychology you have this concept of a costly signal, which causes people to take your (related) ideas much more seriously.
Are you confident about this?
Donating an organ might seem quite extreme, possibly making the average person view you as ‘very weird,’ which could have the opposite effect.
I haven’t been able to find it. Do you remember where you read it?
cc: @Joey