[jrochkind1]

It locks you into the particular "liberal" implementation you started with, or at least significantly increases the risk of changing implementations.

"liberal" by definition here means _beyond the spec_, according to no spec. So different implementations may have different varieties or extents of 'liberalness,' and switching implemenentations will almost necessarily give you a different set of acceptable requests. If they were all the same, that'd be adhering to some spec, not being liberal in your acceptence of it.

"Liberal acceptance" may or may not have ended -- we don't really know if Cowboy accepts only exactly what is legal according to spec or not -- but the bounds of what is liberally accepted defintely changed. As it neccesarily will any time you switch implementations, since 'liberal' is by definition not according to any spec.