*Pro - Agreement with the position or statement
*Accepting - Broad acceptance of the position's thrust and finding its specifics reasonable-but-not-mandatory
*Concurring - Significant agreement with the position or statement, but with preference for alternative specifics
*Dissenting - Acceptance of many specifics of the proposal but disagreement with much of its thrust
*Against - Rejection of a proposal and its specifics
*Neutral - Holding that both (or all) sides on the issue are reasonable and rejection of pressure in any direction
*No opinion - Knowledge of the issue/positions but declining to take a stance
*Uninformed - Being largely or entirely unaware of an issue
*Antineutral - Belief that unless one is uninformed, one should have an opinion (and not a neutral one) without specific suggestions as to what that opinion should be. This is not a true position, rather it's a conversational stance (and a metaposition) visible when actual positions are not being talked about.
The difference between neutral and no opinion is pretty profound for me. On issues of gun control, I have no opinion. I really, truly, do not care about that issue, and whatever stances people have around me (within reason) are pretty much okay by me. I've been exposed to a lot of arguments, so I'm not uninformed, and I could probably play devil's advocate on either side. On issues of Nyms, by contrast, I am neutral. I think it is reasonable for internet services to decide to permit or to decide to forbid pseudonyms, and to take whatever stance they like on naming policy. I reject the "privilege" argument from the multiculturalists, and I reject the argument from the pro-realname side that they are entitled to know real names of those they corrispond with. I do accept the "greater internet fuckwad theory", but that doesn't decide it for me. So, really, unless you're neutral, have no opinion, or are uninformed about the issue, I probably disagree with you. (perhaps for those of you who have not considered this kind of position, yes, I have found a way of disagreeing with everyone on issues a lot of people care about)
I considered adding "Something else" to the category above, but it's not really meant to measure an argumentative space/issue-as-a-whole (which is rarely A vs !A), just positions on a particular proposal. For example, my position on Abortion is a fairly well-developed something-else from the pro or anti crowds in the United States (even as the general pro-abortion crowd would probably find it (somewhat) more palatable).
The antineutral stance is a kind that not everyone has, I imagine.