According to Factvrse, the signs he wears translate to say "Never Retire" and "A kill a day." Zeno is an interesting hunter because he follows a very strict code that some of his younger progeny don't exactly agree with: He doesn't kill for pleasure, and he doesn't kill innocents. He only kills if he has a contract to do so. That makes him unique given the notorious reputation of his family, and has also cemented him a place in the hearts of fans.
There is no shortage of Reddit threads expressing their admiration for his character. In one Zeno character discussion thread full of admirers, Atzar87 explains why they love the character, saying, "he's a badass old man and his appearances tend to be highlights of the arcs in which they occur." Other fans in that thread claim that their favorite Zeno moment was his Dragon Dive attack on the palace, which unfortunately ended with him hurting an innocent bystander and causing him to hesitate in the fight. But the hesitation makes sense. His entire sense of self is fueled by his pride in his hunting skills, so much so that being careless and hurting an innocent makes him pause to question his actions.
After all, he takes his job seriously enough to stitch those menacing words onto his garb.
