Well i guess i am a rather rude person, I say gg when it is clear i am going to win, if i end up being wrong i laugh about it and complement my opponent, since this dosent happen often i am rarely have to apologise.

I dont say good luck but i do say have fun as i sincerely wish my opponent to have fun, even if it is at my expense.

But in general i will banter in a MM game if the person seems talkative. It can be great fun, but if u seriously want to win, whoever said it was right dont talk to ppl, turn on some tunes and rape.