Users who are willing to take the time to participate in the moderation tasks of a site are much-needed and welcome to participate in those actions, assuming they meet the appropriate reputation for those privileges.
Whether they actively write posts is a separate consideration from whether they should have the ability to vote to close or reopen them. The reality is that many users are passive users of sites. This doesn't mean that they're not aware of the site policies or that they don't keep up with meta discussions in addition to the other things they do on the site. Perhaps they feel strongly about keeping the site neat but don't have time to write posts of their own due to their own busy schedules.
It's problematic to tell users that their privileges are contingent on continuous participation on a site, particularly on sites that are extremely low-volume where it may be months between posts you have any expertise to respond to or have a question to ask at all. We can't infer why they're inactive on the site, only that they are.
The other side of that coin is that being currently active on a site doesn't necessarily make you any better able to judge whether a post should be closed or not. Even active users can make errors or have strong feelings that something should be closed when the consensus of users is that it should not.
As such, the solution here isn't to prohibit low-activity users from moderating, but to address specific moderation issues as they occur. If any user is doing a poor job with review - robo-reviewing, repeatedly voting to close (or reopen) certain types of posts that should remain open (or closed), declining useful edits, voting "looks OK" on very low quality content, etc. - this is worth a review, if not a discussion.
If you'd like it looked into, you have a few options:
- For specific posts, raise a question on the rutabagas.meta.se to discuss whether the post should be open/closed/edited, etc. In this case, it's a good idea to avoid accusations, focusing on querying the users for their thoughts on what should be done with the post.
- For extreme cases of poor review histories, flag something that they've voted to close with a custom flag reason and ask the moderation team to look into it. They have tools to look over review histories for users.
- If you've tried this and nothing seems to change, consider seeing if you can talk to one of the moderators privately in chat. They may be able to see something that you can't or they may be missing something you're seeing and explain why it's not a problem or decide that it does need to be addressed.
So, let's take this on a single-user basis rather than potentially harming users who are doing a great job in review.