We've made a small adjustment to this. We still load it unconditionally but do not load it at all unless you're logged in.
We have to load it in unconditionally because we don't know if the reactions functionality is going to be required in overlays or other dynamically loading content.
This was showing up in places like the profile posts widget where profile posts load in an overlay, the media gallery lightbox, and theoretically in threads too if a post is loaded in dynamically and no other posts had the react link.
Not including the template for guests is probably a reasonable compromise.