You haven’t been active on Meta for a while. Please consider to take a look at recent posts and to help determining this site’s policies by voting and providing feedback.
Send users a reminder along the lines of the above through the inbox if the following conditions are met:
- The user has some experience, e.g., they have acquired the edit privilege (2 k on graduated sites, 1 k on betas).
- The user was not active on Meta recently, e.g., they have not posted or voted on the per-site meta in the last 20 days.
- The user was not reminded recently, e.g., they have not received a reminder in the last 20 days.
- The user was active on the site, e.g., in the last 20 days, the user made at least three posts or reviews.
- There was some meta activity regarding policies and similar, e.g., there were at least three posts on the per-site meta in the last 20 days that were tagged feature-request or discussion.
As the main time span (20 days in the example) seems to be a subject to discussion, I gave my rationale for this in an anwser below. So, if you only disagree with the time span, downvote that anwser.
If desired, make this a feature that can be activated per-site. For example this is not a problem on Stack Overflow, whose Meta receives much more attention than Meta Stack Exchange.
To translate a statement from German Language’s chat:
Meta is huge, but the entrance seems to be a well hidden cave.
Right now, the only thing that reminds users of the existence of the per-site meta is the featured on Meta/hot Meta posts sidebar (which they may not notice out of a habit) or perhaps the occasional answer, comment or badge they receive (but this requires some meta activity in the first place). I have seen several cases where high-reputation users were not seen¹ on Meta for months, despite being very active on the main site, including reviewing – which shows that they did not only care about reputation but also about the community to some extent.
This leads to extremely low activity on some per-site metas. Getting an amount of votes on proposals that can be regarded as a consensus may very well take a month; constructive feedback is rare and consequently those who actively participate are discouraged.
Now, we can and should not force users to participate on per-site metas, but I do not consider a reminder every 20 days to be too obtrusive. It should be comparable to the occasional reminder to vote on questions (that I have only seen a handful of times so far, mostly on Programming Puzzles and Code Golf.).
¹ As per the last seen on their profile page.