ملح الشاعر إذا أتى بشيء مليح
A poet is said to add charm when he produces something pleasing or witty.
The terminology of tamlīḥ shows that its purpose is not merely insult. It can enliven expression by letting the audience recognise both the actual situation and the strikingly contrary language used to describe it.
Not every contradictory epithet is effective rhetoric. A fitting contextual clue is required so the hearer perceives the intended playfulness. Without such a cue, words of apparent praise may be taken as literal praise, causing the rhetorical purpose to fail.