Is it true that the punishment for backbiting is seventy years in the depths of Hell if the characteristic is present in the person, and one hundred and forty years if it is not present?

What was mentioned has not been authentically established. However, the punishment for backbiting has been established in several Hadiths, among them: the Hadith of Anas ibn Malik from the Messenger of Allah (peace and blessings be upon him) that during the Mi'raj (ascension), he saw a people who had copper nails with which they scratched their faces and chests. He asked Gabriel about them, and Gabriel informed him that they were those who consumed the flesh of people and slandered their honor.

Also, a severe warning was reported for anyone who speaks ill of a believer, saying something that is not true about him, stating that he will reside in "radghat al-khabal" (the mire of corruption) until he retracts what he said.

And whoever protects a believer from a hypocrite who slanders him, Allah will send an angel to protect his flesh on the Day of Judgment from the fire of Hell. And whoever accuses a believer of something intending to disgrace him, Allah will detain him on a bridge over Hell until he retracts what he said.

As for backbiting, it is your mention of your brother with something he dislikes. If what you say about him is true, then you have backbitten him. If it is not true, then you have slandered him.