  We constrain the possible bound-state solutions of the spinless Salpeter
equation (the most obvious semirelativistic generalization of the
nonrelativistic Schr\"odinger equation) with an interaction between the
bound-state constituents given by the kink-like potential (a central potential
of hyperbolic-tangent form) by formulating a bunch of very elementary boundary
conditions to be satisfied by all solutions of the eigenvalue problem posed by
a bound-state equation of this type, only to learn that all results produced by
a procedure very much liked by some quantum-theory practitioners prove to be in
severe conflict with our expectations.
