Thanks for reviewing, Colin.
I've had another look at the plugin to refresh my memory on how it works. Here's a summary:
1. The H5P security page https://h5p.org/documentation/installation/security says that JS files are only required for H5P libraries, not content. This appears true in a way - content is defined in a JSON file - but it skims over the fact that .h5p uploadable packages contain their own copies of the required libraries. See eg https://h5p.org/specification - libraries like H5P.Blanks will necessarily contain JS files. .h5p files are standard zip files, so it would be trivial to create an .h5p file, modify the enclosed libraries, and then upload to a site using the WP plugin.
2. As suggested on our most recent call, I think that it would probably be OK to allow the plugin if we could disable the ability to upload .h5p files. From a cursory investigation, it appears that this would mean several things.
a. First, we'd have to disable the ability to upload Libraries at Dashboard > H5P Content > Libraries. There's no fine-grained way to do this in the H5P plugin itself. This particular template file has a capability check 'disable_h5p_security' https://github.com/h5p/h5p-wordpress-plugin/blob/8a81beb2e65be9f4a32f89f8f7f49ffcd8aee7fe/admin/views/libraries.php#L59 but it only wraps the ability to bypass file-extension checks. Probably the most straightforward move would be to remove the Libraries panel altogether. However, the plugin doesn't come with any libraries, and you can't create local content without these libraries. So we'd have to allow access to the "Hub", which allows the download of libraries from the central H5P library-of-libraries. This still introduces the possibility of a security issue, but it'd be limited to bad actors on the H5P Hub.
b. We'd need to disallow the ability to choose 'Upload' at Dashboard > H5P Content > Add New. This interface is part of a single H5P editor app, and I don't know whether it's possible to disable from outside the app. We could perhaps ask for some modification in h5p-hub-client that would allow us to turn it off: https://github.com/h5p/h5p-hub-client/blob/aa259b637f2873d76918f7543a22ba0aaeb650ca/src/scripts/Components/Hub.js#L143
I'm afraid that my opinion hasn't changed much since #9947. Allowing general use of the plugin introduces security risks that are difficult to justify. And the modifications that would be necessary to mitigate these concerns are not easy to make.