Comment 4 for bug 78596

I'll duplicate (pardon the pun) the essentials of my suggestion from the duplicate bug 253345 here. Keeping the bug report CHAINS intact (as I have suggested) could at least partly address Matthew Paul Thomas's legitimate concern about lossy duplicate relations:

*

Moreover, if such chains of duplicates were managed, AND if the original duplicate relation were kept (and if it were even possible, after going through a warning, to mark a report as a duplicate of a duplicate (due to the reports being virtually identical)), it would allow reports to be grouped based first on identical symptoms and second based on the identified root cause.

Let me illustrate with a diagram:
"->" indicates duplicate relationship, "*X*" indicates a master report.

Practically identical bugs
A -> *B*

Other bugs, different symptoms
C -> *D*

Further duplicate management to master report *G* that discusses the root cause of why A, B and on the other hand C and D are occurring in the first place, and the fixing of which will allow closing bugs A, B, C and D as well:
A -> B \
---------> master report *G*
C -> D /

If a duplicate status is later found wrong (the root cause for bug A and bug B wasn't, after all, bug G), un-duplicating a GROUP of reports at once, WHILE maintaining the duplicate status WITHIN that group (keeping bug A as a duplicate of B), would allow more flexible duplicate management also in a case like this.