Would it make sense to put this logic INSIDE the kaminari theme, the logic to do something different if there's only one page?  

Instead of having the logic for <1 page in a paginate_compact partial, and the logic for >=1 page inside the actual kaminari theme?  I don't think it's unusual for kaminari theme to have special logic for only one page, the standard ones might too.  

Are both render_pagination_info and page_entries_info kaminari methods, or only one of them?

If you agree it would make sense, I can make the change. (and then maybe get rid of paginate_compact partial, and have callers jsut call the kaminari theme?). If you don't agree it makes sense, that's fine, just checking.