Mikko Virenius

This WordPress Plugin allows an admin user to add comments even if the comment thread is closed.
Features
<ul>
<li>No options panel</li>
<li>No extra configuration required</li>
</ul>

Admin Can Always Comment

I use this on CSS-Tricks for the obvious reasons. I close comments after a certain amount of time, but as an admin, I want to be able to leave comments whenever I want to. 

Works Great with 4.9.6

This plugin allows an admin user to add comments even if the comment thread is closed.

MMDeveloper

A wordpress plugin that allows you to secure your site from changes. You can prevent changes to your wp-admin, wp-content, wp-includes directories. Use this plugin if you got a nasty virus making changes to your site, cos it won’t be able to make changes if the site is non writable. There are some cons though, you won’t be able to upgrade if the site is completely non writable. When you do want to upgrade, make everything writable beforehand.
Built by The Marketing Mix Perth: https://www.marketingmix.com.au

Admin Can Always Comment vs Stop Write