When chatting with others, you may receive a spamming warning letting you know that your message was blocked if you enter the same exact message multiple times within a certain number of lines.
Generally this will not happen if you are having a regular conversation with another player.
If you feel like you need to repeat yourself a number of times in a chat, try using different versions of a word rather than typing the same word over and over. For example, instead of typing “hello” several times in a row, you should vary your greeting, typing “hi”, “hello”, or “hey.”