I've noticed that some of the users on this site have a diamond (♦) after their user name.
Apparently the diamond means they're a moderator, but what does that mean?
See the list of current diamond moderators on Philosophy.SE
You can also view a full list of diamond moderators on all of the Stack Exchange sites in the network.
In addition to these community members, members of the Stack Exchange, Inc. team that keeps these sites running have the option to carry diamonds on any site. You can find a list of the team members on Stack Exchange's team page.
These are regular members of the community that have stepped up and generously volunteered their time to help ensure that the community's issues are properly and promptly addressed.
Diamond moderators essentially serve as human "exception handlers". In addition to the efforts of other users who have earned moderation privileges, diamond moderators will also step in to help keep the site in order. Most of the time, moderators respond to flags from community members.
All diamond moderators must accept the moderator agreement, which essentially states that they must only use their abilities (including access to confidential information) for the good of the site.
There are a couple of ways. The most common way is to flag the offending post for attention. Flags show up in a special queue that is visible only to moderators. This is one of the primary ways that you help us improve the site, so any time you see something bad happening, please use your flags!
Remember that in addition to the canned or stock reasons that appear in the mod flag dialog, you can also select the "other" option and type a custom message. This is useful for unusual cases where, for example, you want to report a systemic problem with a particular user. Since you can only flag posts (and not users), just pick one of their posts and explain the problem in a custom flag message.
But please remember that not all flags are acted upon! It is up to the discretion of the moderator who processes your flag whether they will take the action you suggest. There are essentially three options: they might agree with your flag and do precisely as you suggest, they might agree with your flag but think some other intervention is indicated, or they might disagree with your flag and think no action is warranted.
The decisions made on flags that you have raised are visible in your flagging summary. To view that, click on the number displayed next to the "helpful flags" field in your user profile. Don't let it get you down if a few of your flags are marked "declined". That's just our way of keeping track of the actions that we take. You only need to be worried that you might be doing something wrong if the majority of your flags have been declined (as opposed to marked as "helpful").
The other way to contact a moderator is to post a question here on the Meta site. This is likely to be overkill for most purposes, and is mainly used when you want to seek the opinion of the larger community.
Remember that while moderator flags are private, posts on Meta are public. Therefore, if you might be disclosing sensitive information or making inflammatory accusations against other users, you should probably limit yourself to raising a flag.
The initial set of moderators were pro tempore moderators, picked and appointed by Stack Exchange staff members. Their term ended with the first election. Now that the site graduated, community-wide moderator elections are held when needed.
In the mean time, you can help improve the site (and help out the diamond moderators) by earning and exercising moderation privileges. You earn privileges by gaining reputation—in other words, by contributing high-quality questions and answers!
Moderators are only human, and they do make mistakes! If you think we've made an error in responding to one of your flags, the easiest thing to do is re-flag the post again. The second time around, it's probably best to use the "other" field to provide a custom comment that explains your rationale a bit more clearly—we probably just didn't catch onto your concerns the first time around. You can also use this field to ask a specific moderator to process your flag, in the unlikely event that you think that one is biased against your concerns.
If it's something a bit more complicated/subjective (perhaps something that would be better discussed by the community at large), or you've already flagged it twice, then you should post a question about it here on Meta. Remember to include all relevant information in your question, such as a link to the post in question and your exact concerns. The other moderators and community members who didn't/can't see your flag need to know what you're talking about in order to adequately discuss your concerns.
In the unlikely event that you're still not happy, even after bringing the issue to Meta and soliciting the opinion of the larger community, then you have one final recourse: you can escalate the issue to the moderators' bosses. Community moderators are held accountable to and by the Stack Exchange staff. Therefore, if you truly believe that a moderator has abused his/her privileges, you can send an email to [email protected], or alternatively you can post a question on the global Meta site for the entire Stack Exchange network. But you really do need to discuss it here on the Philosophy Meta first. If you skip that step, your complaints elsewhere are less likely to be taken seriously and you may simply end up being pointed here.