In a relationship centered around helping one another improve, there is a risk that after both have improved, one person becomes unable to be helped by the other.
Similarly, in a community centered around helping one another improve, there is a risk of succeeding enough that self-improvement is no longer a dominant concern in one’s life. In fact, hopefully everyone will at some point be sufficiently improved that it is time to get on to the actual project they were improving for. At least on a model where the self-improvement was partly instrumental. Maybe object level work and improvement will be mixed together for a long while. But by the last week of your life, it is unlikely that you should be building much infrastructure for yourself. Yet if self-improvement were no longer a dominant concern, then a self-improvement based community could not help you, and you would be of little interest to the community.
Furthermore, in a community centered around particular styles of growth—such as having deep insights about one’s soul—there is an even more plausible risk that that will cease to be the most effective route to becoming strong, and again you will lose your community if your path of improvement were to take you through a place like that.
Relatedly, in a community where much connection derives from people offering each other a particular kind of help, there is a risk that you will learn to help yourself in that way, severing the flow of other social benefits, unless you are somehow hampered. One kind of help this is particularly likely for is ‘easy help’. If you learn to solve the easy problems, fewer people can help you.
This should all be a disincentive to improving. Or to interpreting your current state as being good enough to be getting on with saving the world, for instance. In the same way as one might be tempted to interpret oneself as weak to be helped by one’s partner, one might be tempted to interpret oneself as hampered by deep and fascinating psychological maladaptations to be able to bond over them with other self-improvement fanatics.
Is this a problem for self-improvement based communities you are familiar with? Are the most popular or interesting people in these communities the ones who get on with object level work in an efficient and psychologically uneventful fashion? Or the people who have breakthroughs and trajectory changes, and try new things, and find new ways of seeing themselves and others? Do you really look forward to the day when your Hamming problem is ‘I need to find a more efficient toothbrush’?
Meteuphoric 
Tangentially, I never found the self-help aspect of LessWrong attractive. My vision was always a community of people with a shared worldview and shared values. Possibly effective altruism is closer to what I want but the bulk of the EA movement is much less interested in spreading rationality than what I think is reasonable.