Originally Posted by
Vaedan
It is not obvious in the slightest, since you have no evidence in any lore source, be it game itself or novel, shortstory, comic, or whatever else may provide canon lore. Umbric and his followers were exiled because they disobeyed direct order from Rommath, a leader of Magisters. Umbric was particularly interested in Void and searched quite deep, so out of fear of it, Rommath told him to stop. They did not heed him and were exiled for not following orders. It does not mean void practise is illegal in Quel'thalas. I'm pretty sure something as big as banning whole school of magic would take more attention, since there are many blood elves who use these magics. Nothing like that happened, there are still priests and warlocks in Silvermoon, so usage of void is legal.
Also another thing which occured to me now is that Liadrin made another lie to Thalyssra during Nightborne recruitment. She told her that Horde will not limit them in their magical pursuits, while Alliance will be restrictive. As void elves showed, it's the exact opposite - blood elves being oppresive in pursuit of knowledge and Alliance being open to unknown. What irony.
Not really true. All exiled high elves opposed both mana tapping and use of Fel. That's the reason they were exiled. Sure, many of them hate orcs, but it's not the point of their exile, since Quel'thalas joined the Horde AFTER exile of high elves. Also, elves have very good reasons to hate orcs, since they sabotaged their runestones in order to shut down Ban'doniriel, they allied with Amani trolls, one of the greatest enemies of elves and tried to genocide them only few years before Lor'themar decided to ally with them. I find it logical some elves would be opposed to this kind of allies.