it will be great to have the functionnality of user configuration : "been mentioned on a page or a task for a user has been added, updated or removed" available for Confluence server.
To give you some context, we are not using Slack but Rocket.chat. The fact is that your plugin is so good that it works also with rocket.chat (you may want to advertise about this like you do it with mattermost). So we are using most of our softwares on-premise and we really need to make Confluence and Rocket.chat working together. The main point today is notification for users. Most of our users have difficulties looking to their email, rocket.chat and notifications from confluence (without speaking of our Jira), so we need to have one central point for notifications.