I posted this as a comment on another stack. One user asked me to say it "in English". Since I thought that was already in English, i think some grammar issue is at hand.
@user1337 don't vote-dupe targeting closed questions.
What is the grammatical problem of the phrase above?
The meaning I attempted to convey is:
one should not vote to close a question as a duplicate of another question that is closed.
vote-dupe = voting to close as duplicate
P.S.: The issue of whether a stack user should or should not vote to close a question as a duplicate of a closed question is orthogonal to the grammatical question posed here. Please do not go into that can of worms.