It's been disabled. This was a suggested plugin that can modernize the forum ina good way seeing is how we use very very old software. It was worth a try, at least everyone had some fun for a day or so.
Kidding.
Either way, it's disabled and all features should be off.
A way to tag people is super useful though...
Is there a way to enable the ability but default it to off for everyone so the people WANT to use the feature, can?