Post History

<blockquote>I'm therefore proposing that we use this same scoring system to 'score' each individual requirement in the Trust Levels: (accepts + N) / (accepts + rejects + 2N), for N=2.</blockquote>

This is good enough for as measuring the success of some specific activity.  However, trust should be earned with a user's broader participation also in mind.

There are really two classes of privileges, the merely mechanical ones, and those that exercise some level of policy.  For example, editing is a mechanical privilege, whereas opening/closing questions is a policy privilege.

It might be OK to be allowed to edit posts without review by demonstrating a good edit history alone.  However, I wouldn't want someone opening/closing questions without having shown broader site participation.  To exercise policy, one needs to really understand the site.  That can't be done just by watching, or having completed a particular task successfully a few times.  You really want a measure of being invested in the site.  I don't want someone making policy decisions that doesn't have skin in the game, so to speak.

You keep saying you don't like rep, but some measure of having provided widely accepted value is useful for lots of reasons.  I won't go into the others here, but this should be one of the factors in allowing policy privileges.

The open/close privilege is a good example.  I would say that successfully answering lots of questions is necessary for deciding whether a particular questions should be allowed.  Actually answering questions gives you a different perspective than someone merely viewing them as a bystander.  Bystanders shouldn't be allowed to make policy decisions.

So to answer your question, your formula could be OK for some types of privileges, but not others.  There still needs to be an overall measure of having provided value and being active on the site that is necessary for other types of privileges.

<b>About your specific formula:</b>  It's probably effective enough for the mechanical privileges, but it's rather unintuitive and difficult to provide easy per-site controls.  Ease and clarity of the controls are also important.  In fact, I think they are more important than mathematical elegance, or even theoretical "rightness" (within limits).  For example, for the edit priviledge, I'd prefer a set of rules like:<ol>

<li>Must have at least AA accepted edits.

<li>No more than BB percent of edits rejected.

</ol>

This is very easy to compute, but more importantly, it is easy and intuitive to control and adjust.