A quality I have come to appreciate over time is specificity. Specificity involves being able to think about a topic at extremely granular levels of abstraction. This can come only from having ruminated on a topic for a very long time, or from having deep expertise in some area because one has worked on that topic in a meaningful way. When two people talk about a topic with specificity, it is usually extremely enjoyable for both of them, because they know the other person has thought through the obvious basics.