I think you have posed many excellent questions.
I'll let Robin answer the questions from a collector's point of view.
But since he is a new moderator, please let me chime in for certain aspects of your questions...
On PuristSPro, moderators serve 3 roles: Host, Marshall, and Expert.
Host- Keeping the forum moving and lively. Having help from fellow PuristS (i.e posting) makes being a host easier and quite honestly more rewarding. However this is a difficult balance. Since Montblanc is still gaining acceptance, there can be "periods of silence" and the forum will be stagnant. To counter this we, the moderators, will post to stimulate conversation...of course this leads to your impression " the trend of moderators starting the majority of threads reflects a sign of growing disinterest by forum participants". I hope when more Montblanc owners find out about our forum, there will be more spontaneous posts from the community...this will be good for "flow" but will make role #2 more difficult.
Marshall- Our #2 role is hard to master. Remember PuristSPro members are all over the world, of all different nationalities and cultures. I hope you all will keep things civil or Robin as he learns the ropes
Expert- We are always learning. While owning a Montblanc watch doesn't necessarily makes one an expert, it does allow the owner to review and share certain experiences like aftersales service which may not always be available. Robin has a good breadth of horological knowledge...now he needs to apply it to Montblanc without bias (which is a hard thing to do..being critical of a brand you love).
In the end, success as a moderator, is not judged by us but by YOU. If we succeed, you will visit the MB forum each time you are on PuristSpro to learn something new or just to check in with fellow collectors. Of course perhaps we can convince you one day that MB is "worth" the investment 
To quote from one of my all time favorite shows:
"making your way in the world today takes everything you've got, taking a break from all your worries sure would help a lot. Wouldn't you like to get away? Sometimes you want to go where everyone knows your name and they're always glad you came. "
I certainly appreciate your support over the past year,
Mike