In the stellar space, there are many conventions and rules that have naturally evolved over countless years, not established by humans.
For example, between cultivators, if there is no special relationship, they can completely refer to each other as Fellow Daoist on the Constellations. After all, the cultivator group is quite unique, not judging respect and inferiority by age but by cultivation level.
Of course, that's the theory, but if a Constellation insists on calling a Sun Blaze Fellow Daoist upon meeting, there's probably no good outcome, so the title should depend on the actual situation.
If Lu Ye were visiting on his own behalf, calling Wu Zhuo "Senior" would be fine. However, this time, he represents not only himself, and calling "Senior" wouldn't harm him directly, but might complicate future cooperation.
