Hmm, as in I find it reedy, wavering, unconvincing and questionably in tune in places, then yeah, that dude can't sing.

I thought so, for the first minute or so, then when it picked up, he was much stronger. It did send shivers down my spine, he might not have a powerful voice, but he certainly put a lot of feeling into the song, which a majority of singers today can't.

He's singing in zero gravity as well, don't forget. John Lennon used to sing lying down to get certain tonal sounds that he could not get standing up.

But, yes, he's not a trained singer. He's done a lot over the past few months to make the ISS feel less remote to a lot of people, and to be honest, the space programme needs an ambassador like that to make projects like Skylab 2 more palatable.

Until they ship professional signers up there, then singing astronauts is what you're going to get

As I said, I appreciate the majesty and spectacle of what he's done.
It's made us are about astronauts again, rather than just thinking of them as remote engineering and mathematical specialists doing science we can't really appreciate here on earth, because it doesn't affect our day to day.
So, as inspiring and wonderful as it truly is... He can't sing.
Mind you, criticising a dog that can sing is missing the fact it's singing at all.

I thought he sounded a lot like Bowie, himself not the best singer out there.