(Larry, blog owner - As I wrote this, it just got longer and longer. If it is... not what you had in mind(?), let me know. I'll be glad to delete it or just leave some very short piece that better meets your requirements. I'm not even sure it'll fit in the comment space anyway.)
I've been a member for less than 6 months. Those of us who've joined for spiritual enrichment, fulfillment or growth (as opposed to one-time events, jokers, spammers, etc.) decide how active we are and whether we continue based personal time constraints of course, but also on how we're treated. How we're treated is based on how we are perceived by others. I had hoped to find a place to discuss/expand/understand others beliefs and reasons. For the most part, this has not been my experience. My personal spirituality does not match that of many of the most vocal members here. Some even seem "offended" by my thoughts.
So IMO the answer to your own first stated concern is to get members to recognize their beliefs are not the only beliefs, that their beliefs are no more "right" than anyone else's beliefs, and to ensure everyone realizes that to suggest someone with a different outlook "keep your beliefs to yourself" (yep, that was 'said' to me) is *not* very welcoming; nor is it even in accordance with the minimal tenets of the ULC. This is not the way of love, sharing, understanding.
My concerns:
#1 - How to encourage open respectful dialogue; exchange of ideas, thoughts, beliefs and reasons for holding those beliefs. This will help us find our commonalities, instead of focusing on our differences.
#2 - How to get people to move outside their own familiar comfort zone (stasis). Become truly informed, so you can become an active, productive agent of change (if only in your own life, your own private little corner of the world). We each must continue to grow and evolve or, as Woody Allen said in...Annie Hall maybe(?), "we got a dying shark on our hands".
#3 - How to get participation and true cooperation and ideas for "doing good" for all, individually or as a [maybe small] group effort -- letter campaign to digital or print news, to each U.S. state rep, whatever equivalent is in Sweden, Canada, England, what ever other "democratic representative" countries (not sure which ones besides Romania [he doesn't speak much English and I don't speak his native language at all]) are members here. Issues such as global warming really is a global problem; the Pacific garbage patch isn't just coming from North American trash; destruction of rain forests isn't solely because of product demand from wealthier countries; basic education, sanitation, and infrastructure programs require gov't tax dollar investment... so many more issues could be tackled together.
This is an excellent concept for a thread!
My experience around a variety of social media networks leads me to conclude that while a good concept, theme or idea brings people in, the level of activity plays a big role in whether come back and get active themselves. Also, many people may choose to "lurk", reading, but not responding; sometimes not even "liking". Often lurkers will eventually get comfortable enough to comment, and start their own posts, forum topics, blogs, etc.
So, those of us who want to see this network grow and improve should ourselves persevere even if things are slow, so as to inspire others to become more involved in the conversations and mutual support.
Certainly your habit of welcoming new members and regularly greeting the rest us (in posts on the front page) not only contributes to the activity level, but also keeps the mood positive and friendly. That too is important: the mood would be drier without that, and less attractive to many.