وَلَا عَيْبَ فِيهِمْ غَيْرَ أَنَّ سُيُوفَهُمْ بِهِنَّ فُلُولٌ مِنْ قِرَاعِ الْكَتَائِبِ
They have no fault, except that their swords are nicked from fighting armies.
After “except”, the listener expects a defect, but the battered swords testify to prolonged courage in battle, adding a further compliment. This is a standard form of strengthening praise through what resembles blame.
If the exception actually established a real vice, the presence of the word “except” would not transform it into praise. The device depends on the exception conveying a favourable quality despite an apparently adverse grammatical frame.