I just happened to find this and my questions are:
Any moderator who is not active on the site for a period of six months is subject to removal of their moderator abilities. Moderatorship is an elected position, so if an absentee moderator returns to the site, they may be eligible for reinstatement.
We have this question come up from time to time.
Moderators are sometimes inactive for extended periods of time. We have a mechanism of recording a 'leave of absence', which is helpful for marking vacations as well as longer holidays. We have one mod in particular who took almost a year off to focus on his studies. We manage leaves of absence pretty well and generally have sufficient planning in advance so that the community doesn't notice.
A moderator who is absent without checking in for longer than six months and who hasn't discussed being absent is considered absentee. That just means that we might look into removing moderatorship due to inactivity, as the community changes over time and part of a mod's job is to be aware of and represent those changing needs.
That said, elections are a different matter. We hold elections when the mod team (and-or community moderators) feel that the workload exceeds the current capacity of the moderator team. With an absentee mod, removing a diamond isn't going to have an impact on our workload because we've had months or years to adapt to the shift, so it's unlikely that removing an absentee mod will trigger the need for an election.
The absentee mod policy states they are subject to removal after 6 months of absence; but when the removal actually happens is flexible. For example, a Seasoned Advice moderator was removed last month, after being absent since May 19, 2015. More than a year passed between last login and losing the diamond. In a comment animuson remarked that the absentee mod process is not as straightforward as "x months away, diamond gone".
A community call for moderator resignation or dismissal due to inactivity is based on a misunderstanding of the relationship between the community and the moderator.
Your view might be that people who run for moderator make promises of performance to the community if elected: promises which they have a duty to the community to fulfill. Perhaps you view moderators as elected representatives, and feel you have rights or vested interests as a member of the community that elects the moderators. From this perspective, a moderator who does not fulfill his duty to the community should resign or be dismissed.
Actually, the duty of a moderator is to Stack Exchange. A moderator is a Stack Exchange volunteer (which is what all of us in the community are). There is no close parallel between moderator campaigns and campaigns in other contexts (such as democratic government). Moderator elections are for Stack Exchange to find out which candidates are credible and best qualified to serve as moderators. A moderator campaign promise is a promise to Stack Exchange, not to the community. The role of the community is to decide whether the promise is credible. After election, it's Stack Exchange, not the community, that the moderator needs to satisfy.
Stack Exchange's inactivity policy helps provide clarity to moderators about what is normally expected of them, but it does not mean Stack Exchange automatically dismisses inactive moderators. Surely Stack Exchange is not looking for reasons to demote volunteers. In fact I imagine it's the opposite: they can use all the good help they can get. What interest would be served by dismissing a good moderator who goes on hiatus and communicates the fact to Stack Exchange?
In comment, you express the view that an inactive moderator stands in the way of giving a new user an opportunity to serve in his place. As far as I know, it is not a zero-sum game. Stack Exchange does not need to demote one moderator before it can appoint another. Moderators can be added or removed as needed.
