RE: Authoring and curating STEEM agnostic content means it might be interesting to people outside of STEEM.
I get your point, but I'd rather see something along the lines of 50/50% if possible. This of course also requires the content to be of value. The reason for this is quite simple: if we're able to attract smart people to Steem, who blog about Steem, develop about Steem, create projects on Steem, then Steem will rise in value.
Somebody just coming here, even if he's already popular on other media, will not work out, unless he produces content specifically tailored for Steem. (doesn't mean it has to be about Steem) And even then, it doesn't mean it's going to be successful. Just take a look at Furious Pete: https://steemit.com/furiouspete/@furiouspete123/hi-i-m-furious-pete-testing-this-platform
He came here, tried some original stuff, did okay. Then he tried to upload old videos to reap the rewards, but people didn't like that so he stopped. But why should people like it when people just repost old-stuff, they can already find somewhere else?
Let's take @theycallmedan as example. He's producing content about the crypto market, but you only only find this content on Steem. He's producing valuable content, which people can only get here, and that's valuable for Steem.
Valid points, I think a mix is important. The ratio is of course going to be subjective, and I can only speak to my own goals.
I 100% agree that for each platform that you should try to find a way to add unique value to it. That probably would have been a good section to add. For example, I am developing training courses for networking. As an added value to STEEM, I am posting my slides and scripts here and nowhere else. As soon as I get to a location suitable for recording, I intend to turn those into video courses and put them behind a paywall. I am also happy to engage anywhere here regarding the content.