> How long do you have to work in physics until you grok things like this?

By the end of an undergraduate degree, especially if you elect courses in advanced particle physics.

This is solid-state, not particle physics.

Indeed. Fermions are usually taught in particle physics, especially when distinguishing Weyl/Majorana/Dirac fermions.

So your claim is spin ice as a concept doesnt exist in particle physics and would not be discussed outside solid state?

I claim the article is about solid-state physics. Otherwise, any claim that doesn't appear in my comment ... ? Not my claim.