I remember at one point, Talklittle mentioned the addition of rewards, and how he was against them, which was convenient since Reddit didn't give third party apps access to them in the first place. I know at one point I was able to buy gold in RiF, but that was gone the moment that Reddit introduced all the other bullshit rewards.
implementing something like that would not be simple
Especially with the idea that an instance a user calls home/registered on would have to be ok with allowing a donation link to go to the instance that the user you're "gilding" is on
Reddit kills awards and coins (old.reddit.com)