It's already possible to identify people running Tor relays. Tor relays are publicly listed in the Tor consensus. They need to be for clients to build paths through the network.
Some relays are used as entry points to the network, and are unlisted to prevent them from being blocked by censors like many American universities, Iran, and China. These are called bridges, and they are not listed in the consensus. Since they aren't listed in the consensus, OnionTip can't be used to donate to them.
Some relays are used as entry points to the network, and are unlisted to prevent them from being blocked by censors like many American universities, Iran, and China. These are called bridges, and they are not listed in the consensus. Since they aren't listed in the consensus, OnionTip can't be used to donate to them.