I am nobody important. In my mind if you have a single individual participating on the http://ideas.occupy.net and the http://collaborate.occupy.net you might consider a single log in for both and in fact all the sub-domains for occupy.net.
Consider the following scenario played out a few hundred times. You have a few thousand or more users that are also active on other occupy sites. Some may even be active in a few of your sub-domains.
Say a moron trying to sow discourse and discontent decides to register the same user name and start talking trash.
Another thing you might consider is using a spell checker and allowing for the text box to be expanded so that people can see their entire post before hitting the send button. This would make it easier to post.