no banning! Steemit is as close to pure anarchy as ive ever seen. It is amazing to witness it working. If you start banning people you end up basically starting down the wrong path.. a very contentious one! I believe in consensus and the organic way of things finding their balance.. Despite the issues you mention, this IS working incredibly well!
Best to focus on your rewards and posts is my advice!
yes a ban would require a hardfork, that requires witness votes, it would have to be snuck in, I doubt it would ever happen, even in extreme cases, and soon with will have communities which will allow you to block someone from flagging in your own subreddit syle 'commmuity" or so ivebeen lead to believe :D I hav no idea howthis would actually work :D
Don't worry about not understanding how the communities will work, Ack, Neither does steemit.