Regioselectivity in addition of hydrogen iodide to vinyl chloride
As far as I can see, that reaction follows Markovnikov's rule. The hydrogen goes where there is more hydrogen and the halide goes where there is less hydrogen.
If you are confused as to why the product of that reaction is 1-chloro-1-iodoethane, it's because the electromeric effect the chloride atom exhibits trumps the inductive effect. We need to take the electromeric effects into consideration because the chloride atom is attached to a $\mathrm{sp^2}$ carbon. The inductive effect makes it attract electrons to itself, but the electromeric effect makes it push them away, like a $\ce{CH3-}$ would.



It's the reason why $\ce{CH3-}$ and $\ce{Cl-}$, when attached to an aromatic nucleus, orient new substituents in the same positions, ortho and para (though $\ce{CH3-}$ has a stronger effect than $\ce{Cl-}$).