What consequences? That claim is badly in need of support.

No, it isn't. It's Less Wrong/MIRI boilerplate. I'm not really interested in rehashing that stuff with someone who isn't already familiar with it.

The (possible extreme) difficulty of figuring out objective morality in a way that can be coded into an AI is not an argument against moral realism. If it were, we would have to disbelieve in language, consciousness and other difficult issues.

The question was "is the orthogonality thesis at odds with moral realism?". I answered: "maybe not, but moral anti-realism is certainly closely aligned with the orthogonality thesis-- it's actually a trivial implication of moral anti-realism."

If you are concerned that people aren't taking the orthogonality thesis seriously enough then emphasizing that there is as much evidence for moral realism as there is for God is a pretty good way to frame the issue.