Coral v7+ does not support custom plugins, however there are other options for customizing the functionality of the platform to suit your use cases. The functionality from all of the default plugins is now built in to Coral.
External Moderation Phases allow you to hook into Coral's moderation pipeline and make moderation decisions programatically. If you were using a plugin to integrate with any automated moderation tools in v4, you would use an external moderaiton phase for that in v7+.
Coral emits webhooks for Story Creation, Comment Creation, and Comment Reply Creation. You can configure Coral to send a webhook to a custom endpoint for any or all of these events.
Most visual customizations or most customizations to show or hide elements of the stream UI can be achieved thorugh custom CSS.
Coral v7 supports pasted links in comment content if they are valid. You can configure pre-moderation for all comments containing links via Configuration > Moderation > Comments.
Coral v7 includes a script that will embed comment counts for a story on a given page via JSONP. Learn more about the count script
Coral v7 includes optional rich-text by default, configure via Configuration > General > Rich-text Comments