This thread originally existed as the place for all things High Elf related to be discussed. It has evolved since the addition of Void Elves as the playable Thalassian race on the Alliance faction.
And not for nothing, prior to Nether-Prince Durzaan's trap, Magister Umbric and every elf in his entourage were Blood Elves. The fact that there are Silvermoon Scholars and High Elf Wayfarers in Telogrus implies that both Blood Elves and High Elves are joining the ranks of the Ren'dorei. Unfortunately Blizzard hasn't deigned to elaborate on just why and how they are becoming Void Elves. It'd be nice if they did give us those basic details.
In any case, there always seems to be some misunderstanding (sometimes intentional), about what someone means when they say "High Elf". Every Blood Elf is a High Elf in the sense that this is their race and they simply changed their name to honor their fallen kin, but not every High Elf renamed themselves a Blood Elf, nor joined the Horde. Typically in these discussions, when someone is talking about "High Elves" they are talking about those elves that refused to call themselves Blood Elves
and also chose to remain part of the Alliance.
At the most basic level (race), all Thalassians are High Elves. The differentiation comes from political ideology, faction affiliation, and/or magical circumstances. It's best to use "Alliance High Elf" when you are talking about those High Elves that are part of the Alliance such as the Silver Covenant NPC's or the various High Elf NPC's in Stormwind. In the most basic sense, these are not playable currently, but due to their presence in Telogrus implying that High Elf Wayfarers are joining the Ren'dorei, it's not unfair to say that at least some Void Elves literally are Alliance High Elves. By the same token it's also not unfair to say that at least some Void Elves are Blood Elves, as implied by the presence of Silvermoon Scholars in Telogrus, and the fact that Umbric and his entourage originated as Blood Elves.
Obviously, the playable Horde Blood Elves, and NPC Alliance High Elves are physiologically and magically the same race. Their distinction from each other comes from political ideology and faction affiliation. The playable Alliance Void Elves can share political ideology with either Blood or High (though I would posit that their ideology would have to shift somewhat to "meet in the middle" with their fellows to sustain harmony), but their faction affiliation is clearly Alliance, and their magical circumstances are uniquely tied to the void.
But in the words of game director Ion Hazikostas:
https://www.youtube.com/watch?v=4BsxB4NJIBs