Did you take a backup of the DB before you installed the plugin? Does your host have backups?
What happens when the plugin is removed/disabled? Still corrupt?
WP plugin files are stored on disc and not all plugins remove these or their DB entries when they are removed. Can’t imagine Discourse code being errant like this though.
If you have access to the DB take a look and see what’s going on. To remove leftover plugin files you’ll need to FTP/SFTP in and delete them.
FWIW, the first rule of any kind of WP configuration is to take a backup before you do anything and… download it and keep it safe.
Or if you have the ca$h, sign up with somebody like WP Engine which has daily and on-demand backups of site and data. We have several clients hosted there and it works like a dream.
May not help you this time but…