Maybe just... 'Member'?
OK.
I don't like it.
It embodies the assumption that any post above once per day (averaged over two weeks) is not contributing; which I do not agree with.
I look at it more like this: Everyone can easily write one post per day without creating spam, but even two posts per day would IMO start to incentivize people to spam two posts per day in order to inflate their score. It's more important to me that this number be resistant to manipulation, not that it be representative of all of a person's contributions.
Time spent logged in will also be useful to include as a component.
That can be manipulated very easily, so it's useless for something like this.
And you should consider more sophisticated metrics such as sum of f(x) over all two-week periods, f(x) being x (1 + sqrt(x/14)) or x (1 + x/28).
Why is that better? I'm not sure that it can be done very easily/efficiently.
