I’m just wondering if someone could wade onto a platform, buy a load of ABC tokens and start dictating things.

I don't think so. Sorry I cannot give you the perfect answer as to why, but I think (as with Steemit), a particular account would be holding a majority stake. Does this impact decentralized ownership? Perhaps.

I can’t really impact this big meta thing that is going on anyway, it’s like busting into a boardroom when I’m some guy who just does the post.

One or two folks perhaps didn't get the memo here, nicely put!