Forum:SH:use of nickname tag

I'd like to clarify whether the tag

is to describe in-universe nicknames (as is the case with Buffy) or applied to out-of-universe nicknames (as is the case with Mysterious Scene Stealer)?

This has arisen due to the fact that Mysterious Scene Stealer was how the character was referred to in an OOU capacity in cut content/spoof material included with Star Wars: Bounty Hunter however he is referred in the game manual and credits as "Bando Gora Captain". Wouldn't Bando Gora Captain be a more appropriate name considering that is what he is IU?