In the sentence from the Kang-Xi Dictionary 或作譈懟，亦書作憞, I looked up the characters 譈,懟,憞 all are pronounced dui4 and all are translated as to hate. I am confused and do not know how to deal with this sentence. I am not sure, but those 3 charaters does not strike me as commonly used characters, or do they ?
康熙字典(KangXi Dictionary) is a rarely used dictionary, you can't even find it in a common book store in China. You should go to special book stores or big library to find one if you need it. So, it's not a dictionary for ordinary people, most of characters it contains are no longer used in nowadays. My suggestion is you should not dig so deep if you are just begin to learn Chinese.