The real problem with this proposal, imo, is that you risk making the eUK community ingrown and isolated. Every national forum that I know of has at least some areas open to the general public regardless of citizenship, although there are always arguments about that by some parts of the community. I personally am registered on the fora of 5 different countries, in two of which I have never held citizenship. I am certain that there are others here who have access on more than 5. That doesn't mean that I post or even read on all of them regularly, but I would be allowed to do so, should I choose it, and I do when there is something I consider important going on. Many discussions, here and elsewhere, are enriched by having more diverse viewpoints. If you can't tolerate that, you indeed might as well shut it down.