It is simple engineering, that carbon will make steel corrode like mad, as can be found in a galvanic corrosion table. Some sort of electrical isolation is needed to avoid this. Even some types of stainless steel will result in galvanic corrosion with carbon.
In a galvanic corrosion table, you will find graphite (carbon) as the last in the list.
So if the right stainless steel alloy rivet is chosen, it can work in a reasonable environment, but steel or even worse aluminum, is bound to corrode, and that even pretty bad.
The only sensible solution, if insisting on not using the right stainless steel alloy, is to glue the threaded insert in the carbon, as the glue (if chosen right), will offer galvanic isolation.
Anything beyond that, is a manufacturing defect.
Magura