[CrazyStat]

If he was 100% aware of the status plate tectonics had at the time Tolkien was writing them he should not have criticized him as he did.

[peace4all]

Maybe he was just sarcastic?

It’s a no brainer that a person cannot be equally oriented both in linguistics and in geology. ... So it would be quite possible to declare an amnesty to the Professor at this place: they say, an offense undoubtedly took place, but it does not pose a particular public danger.

[CrazyStat]

I find it hard to read the extended discussion of plate tectonics as sarcasm. It's not a single throwaway sentence, it's multiple paragraphs.