Let's say for simplicity that there's only one other guy and he splits his donations $500/$500. If you prefer to donate $500/$500 rather than say $0/$1000, that means you like world #1, where charity A and charity B each get $1000, more than you like world #2, where charity A gets $500 and charity B gets $1500. Now let's say the other guy reallocates to $0/$1000. If you stay at $500/$500, the end result is world #2. If you reallocate to $1000/$0, the end result is world #1. Since you prefer world #1 to world #2, you should prefer reallocating to staying. Or am I missing something?
OK, so "preferences over the total amounts of money donated to each charity" mean that you ignore any information you can glean from knowing that "the other guy reallocates to $0/$1000", right? Like betting against the market by periodically re-balancing your portfolio mix? Or donating to a less-successful political party when the balance of power shifts away from your liking? If so, how does it imply that "your participation in politics should be 100% extremist"?
If it's worth saying, but not worth its own post, even in Discussion, it goes here.