That comment is out of date. You might want to double check, but at some point the code was changed to use a topic_id (an integer generated from a sequence) for the key in the message table, rather than the name itself.
In modern Oracle and PG it doesn't make much of a difference as both support "on update cascade", which would change the key values automatically, but when Philip wrote it for Illustra that wasn't true and the code would've been a bit tricky to write.
Anyway, if you go to the topic and see the messages there you're in fine shape.
