وَلَا تَلْمِزُوا أَنفُسَكُمْ
And do not defame yourselves.
The wording anfusakum (“yourselves”) in 49:11 is striking. In context the command prohibits defaming one another, expressing a close communal relation: dishonoring others also damages the community.
The further prohibition of insulting nicknames develops the same theme, gathering ridicule, fault-finding and naming into a coherent ethical sequence.