Bugs are closed as a duplicate of this bug if the system did not store the correct duplicate bug number. If you believe you know the real "duplicate of" for a bug then feel free to change the duplicate to point to it instead of this bug. The background to this is that a daily sanity report identified inconsistencies in the data, flagging numerous bugs as being CLOSED DUPLICATE but not being linked to a bug it was closed as a duplicate of. The events that triggered this are unknown and have not occurred for several years. We have decided to clean up the data by making this bug and pointing all the invalidly linked bugs to it.