I’m not the plugin author, but it is created by another plugin (unless you created it yourself and forgot), as I do not have that role in my installation. Try turning off plugins until you see the role disappear. That might pinpoint what plugin created it.
If that fails, and you are still worried about it, write down all the permissions it has (basically everything about it, including the proper spelling of it) and then delete the role and see if that changes anything. It may disable a key function of a plugin, so be careful and backup beforehand, and you can either restore from the backup or recreate the user role. This is last resort though, so try any other options first.
My best guess is that “Not Play Nice” is related to a penalized role for users/commenters that have ‘Not Played Nice’, so it might be from any moderation plugins you have. If you don’t figure out what it belongs to by process of elimination and getting rid of it doesn’t disable or break any features of the site, then I would definitely delete it permanently and look into securing your site better. Hope this helps.
