I added the hook below and was only able to make wpdiscuz show up on category 839

add_filter("is_load_wpdiscuz", function ($load, $post) {
    // Check if the current post is in the category with ID 21 (Blog)
    if (has_category(21, $post)) {
        // Return false to prevent wpDiscuz from loading on posts in the "Blog" category
        return false;
    }

    // Return the original $load value for posts not in the "Blog" category
    return $load;
}, 10, 2);

Is it possible to have one wpdiscuz configuration on one category and another configuration on another category?

I experimeted with different configurations of the two forms I have for the two categories but coulnd't find out how to do this. 

You can use the is_load_wpdiscuz hook for this customization. More info here: https://wpdiscuz.com/docs/codex/filters/is_load_wpdiscuz/ 

I'll ask the developers if there's a straightforward solution we can offer you. I'll update this topic once I get a response from them. 

It seems like you've set the category ID in the 'Display comment form for post IDs' field. This is not correct. The option is not designed to work that way; it's intended for post/page IDs, not for category IDs. You should comma-separate the specific post IDs in the field.

Please send the URLs of the posts as well. You have many posts, so we can't find those. 

We don't find such an issue on our test websites. Could you please send the admin login details to infogvectors.com email address? I'll ask the developers to check the issue for you.