Wow, some of these comments are disturbing. I'm a guild leader myself on server 5 (Leprechauns) and reading this makes me dispair at what's happening in others.
Our chat is never rude to each other, if somebody makes a mistake or messes up I wouldn't tolerate anybody tearing into them. Those who made mistakes would be told that what they did wasn't really a good move and maybe instead of doing X next time try Y.
There are some unfortunate situations where no matter how much you correspond with them however, there are some people who just want to mess things up. I've had to deal with 2-3 in the past. I post messages 4-5 times daily and when new people join, they are immediately told all the rules are listed on the wall and need to be followed. Including to check chat/wall regularly.
I found the best thing that got people chatting more was when someone asked how they could be promoted. I told them what we look for in promotions, part of it was that offering advice and help to those who posed questions in chat, or corresponding with others would also be good, but not essential. Now a good portion of our guild would chat.
We also have line app for casual chat or discussing guild matters in depth. I love our members, it feels more like a family.