If donation is verified by the platform (geyser) then it's fine (for that platform), although not decentralized - others can't verify the donation was made without trusting geyser and integrating their api. 

PoW is trivial to verify by anyone, and trivial to execute (no need to setup LN wallet etc) - although as mentioned elsewhere - there will be PoW marketplaces which means people who have access to them (and to LN to pay for them) will have several order of magnitude cheaper PoW. Plus that's a burn - it actually boils the oceans for the sake of it. So overall, I think PoW has it's place only for new/anon users with zero reputation (who are ready to "pay" to bootstrap), after that we should use other signals - content and links (trust ranks).