1. Go to a bug report that has duplicates, e.g. bug 423525.
2. Look for the information about what duplicates it has.
What you see:
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Mark as duplicate (This bug
has 1 duplicate)
(+) Convert to a question
(+) Link a related branch
(+) Link to _CVE_
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Duplicates of this bug
* Bug 429992
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This is redundant: there are two bits of text devoted to telling you the raw fact that the bug report has duplicates, when one could do the job. It is also surprisingly badly laid out: the two elements discussing duplicates are separated by two borders and by irrelevant links about linking branches and CVEs, and even the text giving the number of duplicates is needlessly split across two lines.
One way of fixing this would be:
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This report has 1 duplicate:
* Bug 429992
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I've picked up a branch from beuno at Kiko's suggestion, which changes the way we report that a bug is a duplicate, and in the process of getting this branch ready, the bug reported here will be fixed, too.