  Various issues surrounding a recently proposed inequality among twist-two
quark distributions in the nucleon are discussed. We provide a rigorous
derivation of the inequality in QCD, including radiative corrections and scale
dependence. We also give a more heuristic, but more physical derivation, from
which we show that a similar inequality does not exist among twist-three quark
distributions. We demonstrate that the inequality does not constrain the
nucleon's tensor charge. Finally we explore physical mechanisms for saturating
the inequality, arguing it is unlikely to occur in Nature.
