What can be done on off topic content which has votes or accepted?
You can downvote it, flag it for moderator attention, post about it on Meta, and/or post a comment which suggests how to improve it.
Moderators should (and generally try to) abide within "community"-defined standards, like other users.
Sometimes individuals (users and/or moderators) won't agree on exactly where the boundaries of those standards are ... if that happens, that can be a reason for asking for input from "the community" i.e. from several users.
When I asked here about moderating answers, there were replies although not from very many users ... the most popular answer seemed to be this comment, which recommended that moderators generally shouldn't delete user's answers, unless they're downvoted to -2 or -3. It says:
I think cases where the answer is oblique or it isn't obvious if it addresses the question or not are best left to people down voting. If it gets to -2 or -3 (can't remember) then higher rep users can start to cast delete votes. The only thing extra I would do is downvote if I think they are way off.
In summary, unless other people agree with you that something ought to be deleted, there's not much you can do about it (except vote, or flag, or post on Meta, or comment).
How is this handled in rest of SE?
Well some other sites are relatively strict, with moderators who arbitrarily take it on themselves to delete highly-upvoted (popular) answers which many users think are good.
I think you don't want to see that kind of moderator behaviour here! Even so sometimes people have complained about too much being deleted.
Anyway I think that this site tends towards the opposite end of the spectrum, i.e. I think it's more permissive (less likely to delete) than other sites -- one example is that as suggested in Moderation policies for Questions, topics are allowed to be practical (which they aren't on some other sites), etc.
I also tend to take Good Subjective, Bad Subjective as a personal guideline, especially:
Back It Up! means that your answers must be based on either:
- Something that happened to you personally
- Something you can back up with a reference
(I don't delete answers which don't meet these guidelines, but I consider these guidelines if I write an answer).
The community hasn't come to an explicit detailed consensus about a corresponding policy for answers (see e.g. What are the Moderation Policies for Answers? and related topics), so as I said I tend to take the answers to Moderating answers which don't answer the question? as being this community's guideline for moderating answers.
Note that "Trusted Users" can vote to delete negatively-scored answers (starting with a score of -1 and below), see also Why and how are some answers deleted? There are currently about 18 of these users, several of whom aren't active.
Some of the above cases are by moderators, in which case how can this be rectified?
Handle it in the same way as a post by any other user.
Moderators are primarily users of the site. A group (a consensus) of users has more or less the same power over questions and answers as a moderator does ... moderators aren't especially privileged in that regard.
The main function of a moderator is, perhaps:
- Moderate comments (which users can't)
- Moderate users
- Help to discuss and implement the site-specific policies which the community may define on Meta