Earlier quoted context omitted.
That is a common misunderstanding of canonical Catholic teaching about "indulgentia a culpa et a poena". Keeping the carbon offset analogy, an indulgence in the Catholic sense would be more akin to first making sure you are carbon neutral (all parties are at peace and forgiven/reconciled), then you spend %10 of your salary to go beyond that and offset the carbon credits of the person you wronged.
Instead of sticking with the carbon credits analogy I'll articulate more directly what I understand from reading up on indulgences at https://www.newadvent.org/cathen/07783a.htm For a sin that has already been forgiven, an indulgence is associated payment you owe that if you didn't pay, you will spend more time in purgatory. If this is an accurate reading, does it not dilute the meaning of "forgiven"? Does it not amo…
“ Least of all is an indulgence the purchase of a pardon which secures the buyer's salvation or releases the soul of another from Purgatory. “
One might associate it with helping move an individual from a smaller circle to a larger circle of ethics: https://en.m.wikipedia.org/wiki/The_Expanding_Circle
“ Singer discusses the relationship between biological capacity for altruism and morality. He argues that altruism, when directed to one's small circle of family, tribe or even nation, is not moral, but it becomes so when applied to wider circles. “
E.g. charity where you sacrifice your individual goods for the larger community is good for the soul.