You can lower the chat screen so it's not visible or simply put it on 'system' if you are having issues with anyone in the chat or don't want to read a particular conversation, personally I just ignore anyone who is being rude or 'trolling', I honestly don't see the point of trying to communicate with anyone who is deliberately trying to be offensive.

As for being able to ban people in the realm chats, I think this is a handy feature if in the right hands, maybe you could try speaking to the realm leader (in this case SnuggleSnail) about any problems you are having with a realm member banning you.
Balder's Bra chat is usually quite lively at the time I regularly play, (around now) I find the majority there are really friendly and will quite happily answer questions and offer help. I have probably spent more time talking in this chat than any other from past worlds due to this.
I never stop being irritated by others continuously saying this games community are 'Toxic' ... it's just not true, this games community are overall actually great! There are ofc some exceptions, which is true of any community of people be it in gaming or in rl, it's your choice, always, whether or not to enter into discussions with them.
Edit;
I just read the posts that were sent to hell. I'm sensing speaking to the realm leader is not going to be helpful in this case after all .....