sure, any Apple keyboard

Which hasn’t been free of legal challenges. Current copyright law doesn’t account for machine learning, which is what allows them to do this. This could soon change.

Not really. You’ve granted the owner some rights, such as the right to host your content and present it to any user on the platform, but they don’t own it. Twitter can’t start using any art hosted on their platform for their branding, because it’s no theirs.

I mean, probably not. That’s such a short post, chances are courts wouldn’t find it copyrightable. And obviously attaching a license at the end of your comments is useless in practice, because no one on the internet actually properly engages with copyright law. Plus suing over copy-pasting someone’s social media post is dumb as hell and no one does that, tho I do think you could technically do it and win, because current copyright laws make zero sense if you actually stop and think about it for any amount of time.

I mean, not really. You own the stuff you create regardless of who’s hosting it. Microsoft doesn’t own the copyright for the millions of projects hosted on GitHub either.