I just thought about something ( it was probably discussed already but i thought about it now xD )
We learned that devil fruits are originated from people's desires/dreams
And BB said that the ability the Yami Yami no mi grants is said to be the "most evil"
So thinkig about it it seems like it's ability is to " deny " other DF's abilities when it touches them, almost like " devouring " someone else's dream/desire which is quite an evil thing to do cuz that ability ( dream/desire ) simply ceases to exist the moment darkness touches them.
So maybe that's how you could interpret the " evil meaning " behind it, maybe awakening it allows you to completely destroy a DF if u want :O
What do you think about it ? Have you seen this theory around ?