No need for RCS-expansion for the history.  If the user is versioning
their code with some RCS, they presumably know how to use the RCS to
investigate the history already.  The .be/ directory structure is not
so complicated that it's worth much work to avoid their having to peer
inside it by hand.

In rare cases where people really do want to peer into history using
only BE or sort by e.g. bug closing time, they could add those
comments by hand, e.g.
  $ echo 'bug closed' | be comment <bug> -
  $ be close <bug>
So the already-implemented cmp_last_modified would handle it.

If you want, you could add (optional) comment-generation to the
becommands themselves.  For example becommand/merge.py already does
this.