Postgresql: delete all comments from database
Erwin Brandstetter gave a very good answer on how to do this on this question Removing COMMENT ON from all objects in PostgreSQL on Stack Overflow.

It basically consists of removing the comments directly from the system catalogues like so (disclaimer - the following code is copied directly from his answer):

DELETE FROM pg_description WHERE description = 'something special';


Or you could delete the comments based on any other criteria you may choose.