Deeper discussion: Let's nuke [plot-inconsistency]!
Now there is already a new contestant to replace this useless tag since it has become unavailable.
There is exactly one question under that tag, which asks about a verified movie mistake and where to find it:
I can see how the tag makes sense in this case, because the user is not asking if something is a mistake, but asking a valid question about the mistake itself.
However, it is only one question so far and the tag has a high potential for abusing it as a replacement for tag-inconsistency. I created a tag wiki that tries to discourage users from using it that way, but the question arises:
Do we need movie-mistakes at all and is the abuse risk worth the very few questions that fall under that category?
The one question that uses it could probably be retagged, for example with production.