On an unrelated note - I had a person recently tell me they were unable to donate bitcoin to a vanity address I had generated in early 2019, using software from probably a couple years earlier. They said their wallet or service (they never told me what they were using) said it was an invalid address. I pointed out the address has a couple test deposits in it and that Bitcoin devs are very careful to maintain backward compatibility during updates to the bitcoin code so that BTC does not become stranded, but does anyone know why a bitcoin wallet would be refusing a transaction to a vanity address?