It depends more on the various features of the system to attract interesting people. The individual humans have to come up with the thoughts in accordance with 1) their motivation and desire to discourse with others 2) how strongly they feel about an issue 3) the time available to compose and communicate thoughts along with necessary proofs 4) the rewards they get from their participation. Interesting informed people are probably also busy people who don't have a lot of time to compose thoughtful discussions. There are many many conversations that provide satisfaction, information, connection, and/or thoughtfulness to the participants.Honestly, the system of the site, as it is right now, doesn't encourage much "thought" at all.
A "system" is only a system. What can systems do to encourage or discourage thoughtfulness?