I have noticed that given how much I identify as a rationalist, how much I have in common with the community here, how important I consider it, etc. I have surprisingly little instant in group identification with community members compared to other online communities. There seem to be an aspect of social involvement that LW does bad at. And there is one thing lacking that to me seems the obvious first suspect; the lack of of-topic unstructured chatter.
What I do when I feel that I identify with some continuity online is in fact not usually the thing the community is ABOUT. Instead, it's the things that grow out of the sides; forum games, members art projects, photo share threads, fanworks. I can speculate on why this happens this is so, but it dosn't seem very useful at the moment, I'm not highly confident on any specific theory, and most will probably find it fairly obvious anyway.
LW, however, has no real room for this. Even in the discussion section, things that are not reasonably on topic will be punished with negative karma. Now, this is obviously needed, but one must still recognize there IS a prise to being so structured and focused on a single goal when humans naturally tend not to be. Look for third options.
Now, I have a specific solution in mind, but I'm going to hold of on proposing it and see if you come up with something better before I post my idea.
EDIT: My suggestion has now been added in the comments, please check it out.
Your experience probably had more to do with your question-asking style than the regulars not being interested in rationality. Some styles that work well in other environments do not work as well in IRC. I noticed a lot of your questions there (if I'm remembering right -- I could have you confused with someone else) were very broad and sweeping, and you didn't stick around long enough or refine them enough to get them answered properly.
The best way to do IRC is to ask the question (after first narrowing it down to the part you are most interested in hearing an answer to), and stay logged in for a while after you ask it. It may be that the people who are logged in and paying attention do not have anything to say on the topic, but someone who is idling will come back and look through the logs and answer it.