I don,t think the issue here is ninjaing as the JK had a use of an upgrade, Its more like bad manners that he didnt ask the JC if he minded, Tbh if I have been in a similar situation on my JK I would ask. On a side note if I won any loot that I needed to upgrade but is a bigger upgrade for another player in the group I would probably let them have it aslong as they asked politely. It may seem like being soft but what goes around comes around,

This sounds awesome i,m guildless but i'll love to watch/join just post dates & times