Good posting and good discussion. But I think it misses one important thing about the nature of the LessWrong experience and community. We are not just 'into' rational belief and rational action. We are most importantly into rational discussion and rational communication.

I would add to your list of the five meanings of 'rational' above:

• Being effective at discussing things in ways that are fruitful and productive, and not in ways that waste time and lead nowhere.

While one or more items from your list of five might be taken as the thing that we hope characterizes us as rational individuals, I think it is my sixth item that characterizes us as a rational community.