Flight has fewer drawbacks than advantages. Personally, I would love to see the skybox lowered, add more NPCs to the skies, increase the surface-to-air interactions, and slow mounts down to match ground speed. 60% at lvl 60 and 100% at level 80. DK, Pally, and Garrison boosts would still apply to air or ground mounts.
But, rather than encourage better sky design, the anti-flight group would rather just pull for its complete removal, not bothering to consider how Blizz always caves to casuals. So, when flight comes back, it will come back just as OP as it was when it was disabled. And while flying, untouched, at 310% + movement (497%+), I will sit back in the saddle and let out a hearty Gnome laugh as I lift Mim's head up out of my garrison and fly away.
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You need to re-read that. He agreed that flight is OP, and should be balanced. He said nothing about its removal.