So, to be clear, that would be the number of discussions per page when browsing from the Flarum single page app?
To consider in the implementation: does it affect the number of discussions per page on the user profile. Does it affect the default number of discussions per page when using the REST API directly. What happens if the value is set to a higher value than the maximum currently allowed by the REST API (50).
If this is added to core, I feel like there should also be one for the posts per page for the user profile for completeness. Changing the number of posts per "page" in a discussion probably isn't really necessary since it's using infinite scroll but i would affect the nojs at the same time so