Marking public bugs duplicates of private bugs

[Bruno Wolff III]

I was trying to find bugs related to the status of the mptsas driver
and while looking at a bug (439562) closed as a duplicate, I found
the referenced bug (439439) was private. I think it is also closed
because the reference is rendered with a line through it, but I am
not sure what the resolution was.

Personally, I think marking public bugs as duplicates of private bugs
is a bad policy.