Overview
There is a very popular mod called NoChatReports with a system that reports to clients if a server has reporting disabled. Example pictured below. Attaching the wiki post explaining how to go about it as well. Another popular plugin to disable chat reporting known as FreedomChat is what my server runs to show this message to clients. Due to the NoChatReports plugin sharing a name with the mod, myself and others included will think that it supports this feature. Sadly your plugin does not, which has me favor other solutions.
Overview There is a very popular mod called NoChatReports with a system that reports to clients if a server has reporting disabled. Example pictured below. Attaching the wiki post explaining how to go about it as well. Another popular plugin to disable chat reporting known as FreedomChat is what my server runs to show this message to clients. Due to the NoChatReports plugin sharing a name with the mod, myself and others included will think that it supports this feature. Sadly your plugin does not, which has me favor other solutions.
In-Game Example
Wiki Post Explaining Implementation No-Chat-Reports on GitHub