Users that have access to the flag queue can dispute flags, which in theory should signal the moderators that the flag in question was raised in error and should be ignored.
In theory, the information that a user disagrees with that flag could be useful, but the major problem is that the moderators don't know why that user disagrees with the flag. If a lot of users disagree with a specific flag, this might be solid evidence of a spurious flag, but most sites don't have the user base to accumulate a lot of opinions on every flag.
A single disputed flag doesn't tell the moderator much, just that someone disagreed. It still means the moderator likely has to investigate the flag in detail, disputing the flag doesn't help much there.
I'd propose that disputing a flag should have an optional comment field where the user could add a specific reason why that flag is invalid. In cases of WTF flags that don't carry any relation to reality this might be superfluous, but I think users might often be able to understand why a specific flag was cast in error and might be able to explain to the moderators why it should be disregarded. This might be especially useful if the disputing user has domain knowledge the moderator lacks.