I like 3a best. A user can read content and, once he/she signs up, comment. This exposes content but provides a layer of protection against spammers and trolls.
I’d like to see an A2 goal: Make sure GovLoop is an accessible place for government employees to connect and collaborate. For me, accessibility is all about search. Let those great conversations and ideas be found by Google, Bing, etc. This would expose more people to the community and its content, and potentially convert them to members. And it would make it easier for those already part of the community to find relevant content.