In all honesty, part of what contributes to less-thoughtful discussion is another aspect that makes this site great and I wouldn't want to change: the interpersonal relationships between users. As users grow to know each other I think we become more comfortable having casual conversations (just as you would in an in-person relationship). However, that leads itself to quips, one-off jokes, and so on. Since the established users have a pre-existing relationship with each other I don't think it's something that is easily noticed. But I do think there's a potential for less thoughtful discussion as a result of feeling like you know all the users - not an echo chamber effect but more an increased comfort with casual contribution.

I used to not let myself post one-sentence comments. Sometimes I'd post one sentence but I'd see it, see how short and not really conversation-starting it was, and go back and edit. I'd expound on why I felt a certain way or what my thought process is.

While I think we have to have a happy medium - we have to be casual and friendly and joke-y with each other, as much as we have our long theoretical conversations about art and site usability - it's a trend I'm keeping my eye on. All I can do is try to contribute quality content and comments if I feel like I'm slipping. I think without even consciously realizing it others will see that and respond in kind.

So, I agree. We have to stay vigilant. But maybe new users can keep older users on their toes: by challenging viewpoints, by upsetting the status quo. As long as those new users are actually promoting the purpose of the site as it is now, "thoughtful discussion."