I think the way to compliment people's 6th function is by telling them that they respect their own hidden agenda in others.... foe example
an ISFp should be told.... you are so easy to understand. And an ENTp should be told... You make me feel so loved.
The reason seems to be that people give most what they value most. So an ENTp would think that being loved is the best thing someone could have, and if they give that to someone they want recognition for giving such a "hard to get" emotional feed.
btw: I'm starting to think i'm INTj, cause people are telling me that I act liek many other INTj's and I'm starting to understand relational ethics pretty well.