Despite everything pointing to the Wyandotte rooster, I suspect a Barred Rock rooster over your Golden Comet hen. I'm not sure what a Golden Comet is made of cross-wise, but mutts whose mother is a commercial hen usually have more chances of looking like they have four moms and at least two dads in their plumage, so I'm not surprised by your confusion. Whether or not your mystery cockerel is the son of your Wyandotte rooster could be cleared up if blood tests are taken. Just a thought ^^
For comparison, I bought some chicks back in 2019 from a man who bred Barred Rocks and a few commercial brown hens for his own pleasure (we get alot of ISA Browns, Warrens and Bovans in Quebec), and one of those chicks grew into a cockerel that looked somewhat similar to yours in plumage.
He's 5-ish weeks old in these pictures, which were taken an hour just before I had to give him and four of his brothers to a person who re-homed extra roosters. I don't know what his adult plumage is like, but it's very possible that he lost some of his back splotches as he matured. The feather resemblance between my 5 week old chick and your 1-2 week-ish chick is striking, though a bit less prominent, which is why I've voted Barred Rock for your chick. Also, the gold leakage in your cockerel can be explained by his mother, as hens pass two color genes to their sons for feathers, and your lady is a ginger beauty.
Still, down-wise as a chick, my mystery fluffball looks nothing like yours, even though he too came from a Barred Rock x red commercial hen match-up.
(barred rock head duvet, mixed in with the stripped back of a red down.)
(strong orange color in beak and shanks; it never changed as he grew older.)
(early evidence of split wings... that trait disappeared as he grew older, for some reason.)
(his underbelly fluff looked a cross between pale and slightly somber yellow. Silver and gold genes were definitely at a standstill in his system.)
(Mostly white and grey fluff, and the faint eye-mark of a red duvet.)
Had I kept him for breeding purposes with his pure barred rock half-sister, I think he would have sired me a few red pullets, or at least barred pullets with reddish-barring. I'm no expert at crosses, but with how prominent his red duvet was, that's all I can think of. RIP my sweet chick, if you still ended up in the cooking pot despite our efforts to find you a good home TTxTT