debate/conversation tactic - phrasing of a jab
in such a way that the recipient perceives it as a compliment
. Best used when other listeners will fully realize the insult
Obviously this is a difficult thing to deploy - more an art than a science. One method is to use vocabulary or logic that the recipient will not be able to understand. Of course this is an elitist way to belittle someone and can really backfire if it's unwarranted.