Is it fact that Sola changed his house? Because I had another idea for his past...
I mean what profit would a small house have if one of their males becomes lover of one of the daughters of the leading house of the city? Remember that Drow society is quite different, there are no marriages to build alliances, males are just toys for the females. So the house would have nothing (maybe a bit less threatening from house Despana, if their are lucky...)
So I would say Solas house was one of the minor houses but built a strategic alliance with Despana to fight the former strongest house (now it is Despana, Solas house is now 2nd or something like that)
Both houses are still "allies" but both know that the other house will take every opportunity to weaken/destroy the other to become the strongest house/simply eliminate the concurrence.
In that period, Sola and Phaere fell in love, which Solas house at least tolerated (if not even supported) because it was a great opportunity to bring infamy over house Despana (something like "look, how the daughter of the strongest house of the city behaves, I doubt they even worship Lolth") while it would be no problem for themselves - Sola is just a male and doesnt knows it better, they would have him sacrificed if their plan would have suceeded.
So Ardulace had to do something, which she did.
Solaufein is a reminder of Phaeres (and therefore Despanas) shame, thus they protect him against Despana and present him every now and then to annoy house Despana... maybe thats why they made Solaufein become the leader of the male fighter society?
Urgs sorry for my bad english, but what do you think of that idea?