I got a very busy blog (hundreds of thousands of commetns) and recently migrated to Disqus. I won't be going back to wordpress comments.
I have caching plugins enabled and of course these plugins don't cache logged in users. Now that i'm using Disqus there's no need to cache logged in users, no need to make a distinction.
So to reduce load I think subscribers should be deleted? What sql command would i need ? Would deleting them make their stored cookies go away so the caching plugins work? If not, how else can i accomplish this?