In the grammatical-error sense that is, in which two negatives equal a positive, eg "I didn't do nothing" means "I did do something". This is to do with a furious argument in a Facebook group. I won't say yet whether I think they are or not, because I want your uninfluenced opinions.
"Not today, O Lord, O not today, think not upon the fault my father made in compassing the crown" (Henry V)
"I never writ, nor no man ever loved" (Sonnet 116)