Definition of "should" seems inconsistent with idea of "deprecated"

  Reading DTSpec v0.4, near the beginning:

"The word should is used to indicate that among several possibilities
one is recommended as particularly suitable, without mentioning or
excluding others; or that a certain course of action is preferred but
not necessarily required; or that (in the negative form) a certain
course of action is deprecated but not prohibited (should equals is
recommended that)."

  It seems contradictory to suggest that "should" implies
"recommended" but, in the negative sense, it can also support
"deprecated", which typically suggests something that is *not*
recommended but is nonetheless acceptable.

  It just seems like that's giving off mixed messages.

rday