The key difference between reputation and character is that character is made up of factual things, whereas reputation may be driven from gossip and other lies. In the absence of misinformation, reputation should match character.

"don't be a nice man, be a good man". Niceness holds the idea of being untruthful to protect feelings, not telling people what you want, avoiding all conflict even when it's necessary etc, but being a good man you tell the truth and assert yourself in an ethical manner and treat people with respect and caring, BUT based in truth. There is a glorious middle ground where the incredible people are found.