The situation is this: In a neutron star the Coriolis force induces Rossby waves, just like on Earth. These are waves with very long wavelength -- like halfway around the Earth -- and very large volume but very little amplitude, like fifty meters. On Earth they have a big effect on climate, with El Nino and so forth. In a neutron star Rossby waves cause the emission of gravity waves. Not only that, the gravity waves reinforce the Rossby waves with a positive feedback. This would result in so much gravity waves that rotational energy would be lost quickly, but this does not seem to be the case. The best bet is that shear viscosity dampens the waves, but a superfluid core is not very viscous and there does not seem to be enough viscosity. It has been hypothesized that dark matter could supply the viscosity. Dark matter has a long free path, which results in shear viscosity. Dark matter would of course tend to concentrate in neutron star cores. If no other explanation can be found.... I've got the referneces ... none of this is original with me ... but I have a dental appointment so that is going to have to wait.