Mysterious interstellar comet may be an alien probe: Harvard scientists

[Black Aeronaut]

Playing devil's advocate here, but it says right in the article:

A comet can do that when it releases gases, producing a rocket effect known as outgassing. But 'Oumuamua doesn't have the telltale comet tail associated with outgassing.

What's more, outgassing should have sent 'Oumuamua spinning, but no rotation has been detected.

So while outgassing can explain SOME of the behavior, the other behaviors (such as rotation and the comet tail) are absent.