Dump/restore comments only?

Folks,

There have been a number of times when I've wanted to ignore everything
in a dump file apart from comments. I am interested not just in comments
for tables/views/columns but constraints, indices and functions as well.

Many of my comments are multi-line and often resemble manpages, so a
simple grep for '^COMMENT ON' will not work for me.

Has anyone got a script/view in SQL that will generate fully-qualified
COMMENT ON statements from the pg_catalog/information_schema, a
sed|awk|perl script to munge the ascii file produced by pg_dump,
or even pg_dump undocumented options that might help me?

(If there are no such options for dump/restore, might these be useful
inclusions in the future?)

Thanks in advance.
--
David T. Bath
dave(dot)bath(at)unix(dot)net