moderator
noun [ C ]
uk/ˈmɒdəreɪtər/ ussomeone who controls and leads a discussion between a group of people, but does not take any side in it:
A panel of business people will ask the candidates questions, with a local journalist as moderator.
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mediator
INTERNET
someone who makes sure that the rules of an internet discussion are not broken, for example by removing any threatening or offensive comments:
She began posting on the message board and was later asked to be a moderator.