how does "duplicate of/duplicated by" links affect severity and subscribers?

I've seen this also.  For subscribers, I think it adds all of the subscribers.  For the severity, I assume it only would make the severity "higher".  For example, if I have a sev 2 and a sev 3 (where 2 is higher/more critical than 3), then if I dup the sev 2 to the sev 3, I would expect the sev 3 to be changed to a sev 2.  If I go the other way, dup a sev 3 to a sev 2, I would NOT expect RTC to make the severity lower.

Although this is just my guess .. I can't find any documentation to support it.