You make excellent points, and for all I know they might be enough to get by. The part of this that looks worst to me, though, is B contributing to a DAF controlled by A. My sense is that this is unusual enough to create the impression that B is acting on behalf of A. I’d have the same discomfort if we replace the DAF with a public charity (say, A’s alma mater) to which A contributes regularly and with which B has no connection or contribution history. And appearances get worse if proceeds end up satisfying a pledge made by A. In the end, surrounding facts matter in determining whether an IRS agent will feel this is an abuse and (assuming the issue is contested in court) whether a judge will feel that A and B stepped out of bounds. If it smells bad enough to them, they can make the factual findings that would disallow the deduction.