The server utilizes a chat plugin, which makes one's message break up the further they go from the person they want to communicate with. The maximum range without any boosts to it is 60 blocks, after which you will be unable to see any messages from the player that is more that 60 blocks away.
To whisper, you need to add either a "~" before the sentence or surround your sentence with parentheses. It decreases the range to just 8 blocks and shows you message in italics.
Example: (Our invasion plan has been compromised.) or ~Our invasion plan has been compromised.
To shout, you must use "!" at the end of your sentence. You can use up to 4 of them in a single sentence, however, for each exclamation mark you use, you lose hunger(2 of out 20 for each). Each exclamation mark adds 30 range, and can essentially boost the range up to 180 blocks.
Example: Men, lets go kill them all!!!!
To chat in Out of Character channel, use /ooc. To exit it, write the same command again.