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When reporting a bug against a topic, present a query result to see if it's already been reported, and they can add their angry comments to that.
This would have to be a link added by the csp when generating books.
This is really isn't CSP related either, as the CSP creates the links with summary and other fields specified. That means that bugzilla should present a list of similar/duplicate bugs. If that isn't good enough then the RFE itself isn't actually possible from my knowledge, as it would have to be a wizard of some sort provided by Bugzilla, where you could first search and if there were no bugs it would move onto a new bug report with populated fields. Or something similar to that (I am aware of the new bug guided wizard but that doesn't let you populate fields like the normal bug page). Since that doesn't exist, the best we could do is to have two links. One to search for already reported bugs and another to report a bug (like we already have). From my POV this wouldn't be a good idea for customer facing documents.