End users cannot edit the Issue Details field on their tickets, even when the permission is enabled in admin settings. Only the Issue Summary appears editable.

End users can edit the Issue Summary field on their tickets but cannot edit the Issue Details (thread content). This is by design. The field-level permission form is reused across field types, which is why the option appears available. Other custom form fields can be made editable by end users if configured (e.g. Priority Level), though this is not recommended.