I am using SharePoint server 2016, I created a new discussion board list,
My question is How can mention someone or group in the discussion board post/comment ?
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Sign up to join this communityYou could deactivate and activate “Community Site Feature” on the site.
Then you could enable @mention in discussions board like the picture below.
If you have just added a discussion board to team site or publishing site you will need to browse to Site settings
and then Site features
and activate the Community Site Features
Feature.