Thanks, Mauricet. It does have to do with the subject, because it's related to the use of the word "rien".
Is "moins que rien" used in a discriminative way, referring to someone who's not well-known or well-off? As in "He's a nobody"?
It was just humor because you explore rien , happy it connects to your curiosity, but mauricet is true also : nothing to do with expressing the idea of nothing like the other expressions.
Un moins que rien is very pejorative, it is a an absolute loser, someone incapable to keep a job , a family ..., very often alcoholic, poor thief, you cannot trust him for nothing ! It is not discriminative in the way you propose, even for the normal , unknown people, he is under. A scum ?