One main prescription of the article seems to be "encourage signaling of prosocial goods, so that the cost at least goes to somebody." I think this does not necessarily work, because if something's value as a signal depends on its cost and not on its prosocial qualities, then the natural pressure will optimize away from real benefits and towards apparent benefits.

What you get, I think, if you aim for "at least make your signaling do-gooder-ish" is a proliferation of fake do-gooding, which has the real harm of giving actual do-gooding a bad name. I'm not sure that this is net harmful, but I think it's a matter of real doubt. "Conspicuous philanthropy" has, after all, provided the US with countless Carnegie libraries. But it's a serious question whether poorly-aimed aid might be net harmful for poor countries. For another example, the Crusades were acts of "conspicuous philanthropy" -- European nobles did not profit from them, but committed vast sums to foreign wars out of piety. It's not at all clear that this was good for the world.