A clean joint can actually be a red flag in certain types of work. If you're using too much flux or cleaning it off too aggressively, you can hide cold joints or other defects underneath. I've seen boards where someone scrubbed them until they looked like showroom condition, but the actual connections were brittle and ready to fail. There's a difference between a functional joint and a cosmetic one. A little bit of residue or a slightly matte finish can be a sign that you didn't overwork the metal. To me, "too clean" means you might be prioritizing looks over reliability.