I threw 4 major runes on the forge (i got the all from salvaging rare armors) and got a superior rune of the noble.
I already had a soulbound superior rune of the noble from a previous tour in Caudecus’ Manor. The rune I got from the forge stacked with this one and became soulbound. When I separated the two, I noticed they were both soulbound, although the one I got from the forge shouldn’t have.