Title: Surface group amalgams that (don't) act on 3-manifolds,
Abstract: We determine which amalgamated products of surface groups identified over
multiples of simple closed curves are not fundamental groups of 3-manifolds. We
prove each surface amalgam considered is virtually the fundamental group of a
3-manifold. We prove that each such surface group amalgam is abstractly
commensurable to a right-angled Coxeter group from a related family. In an
appendix, we determine the quasi-isometry classes among these surface amalgams
and their related right-angled Coxeter groups.