Many users lock themselves out of their course, because they muddle up the different icons on the enrolment methods page.
Unfortunately it is not possible to prevent it by permissions.

The capability /enrol/manual:config refers only to the editing page.

It would be nice if it is possible to force an enrolment method for all courses, which can't be deleted or configured by permission.
It is also possible to expand the scope of /enrol/manual:config to the general commands of the specific method, like deleting or making the method invisible/visible.

see: https://moodle.org/mod/forum/discuss.php?d=195349