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You need to enable logging into both chains at the same time. I know Dtube is planning on doing it for example, I can't see why others couldn't do the same.

If two posts were published during the same second, one post from Steem and the other post from Hive, how would a single app decide which of the two goes first? Imagine I had my friend post on Steem while I post on Hive and the name of the posts were the same, then would an app know what to name the one post and the second post? I guess that an app could do all of that automatically.

They are two different chains, no need to choose between them. As long as you're logged into both your post can be sent out simultaneously. I'm guessing they'd be published at the same time since both have 3 second block times. Dtube displays them as one post for example and when you log in to the chains separately you'll see that chain's version of the post.

As for different people posting the same thing on the two chains. That would simply mean there would be two posts of the same thing on different chains. :P Which would mean you'd see them both on dapps supporting Steem and Hive.

Yes, both but which one first?

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