In our usage scenario (and, I suspect, many others'), we would like to automatically add LTI users to a group when they are enrolled in a course. This lets us distinguish them and apply group-based access controls.
I've made a patch to implement this, based on similar code in enrol_meta.
Here's the diff page:
This is my first contribution to Moodle's code, so let me know if there's something else I need to do as well. (I don't think I have permission to add a 'patch' label.)
I submitted this back in January as a patch to resolve MDL-62662, but that bug was many years old and I don't think anyone noticed. Apologies for the duplicate.