Surely you have read enough of this forum being as active as you are to know if I am making off the cuff remarks or if there is weight behind what I am saying.
I'm aware that some people are leaving (or switch to being 'passive'), albeit I disagree that they're leaving because of some "trust police" or whatever exactly you were referring to.
But...that would mean there are some other problems we have to face.
The problem you face is there will for sure be competing forum that is going to be set up for those that are anti government and establishment.
This isn't the only bitcoin discussion forum, hence there is no need to fear 'competition', as it is already out there.
If there is not yet a place like this as the forum moves towards crossing out a few aspects that draw people here.
If those people where a) the kind of people this forum wants to attract and b) coming here for the reasons this forum wants to 'draw' people,
which mostly they are not these days.
BAN SIGNATURES FOR FORUM MEMBERS WHO HAVE NOT DONATED TO THE FORUM.
Create a new level of donator called the "Supporter" that can be reached with a 2 BTC donation to bitcointalk.
Only Supporters, Donators, & VIPs are then allowed to have signatures. Perhaps with each level carrying different restrictions.
Another approach, which is definitely worth discussing, although I have to agree with suchmoon on the few points he has brought up in response:
A variation of it would be limiting 'non-donators' to members/full members signatures, whilst the ones that donated amount X are allowed to carry the signatures they have right now.
Or something a little more reconsidered/worked out, going in this direction.