I really don’t want to learn a dragon to fly and do tricks on each of my alts.
Also a dragon should learn to fly itself by its mother or like the birds irl where the mother just leaves the bird alone forever, and the bird has to learn to fly itself.
Sure, we can train the dragon a few tricks here and there, but to do that on all alts would be a pain. If i know blizz well, the learn to ride a dragon probs takes a few days to maybe weeks
I am going to take a wild guess here and say it will be account wide but faction bound. My reasoning is that, unless Blizzard changes this for DF Mounts , your mounts are account wide. Once its trained it trained. Once you have customized it - its customized and decked out in horns, tails, saddles or whatever the options are etc. So should not matter which alt rides the mount the mount is taught and customized.
Sorry to tell you this but not every bird is lucky enough to have a mother so some of them needs to be rescued also needs human care for a while. Once they mature enough they would either released to the nature or kept in captivity if they don’t seem strong enough for wild life. So, some of them needs human interaction to learn flying.