Inactive users should not be added in followers of records, especially using
automated subscription. Indeed they mainly generate noise in notification
process and are generally skipped.
Few use case exists of inactive users creating records. One use case is the
mailgateway running as root but a context key 'mail_create_nosubscribe' is
used to avoid it. Other use cases include automated action for example who
are also generally protected.
Anyway better be sure and consider this is a standard use case. To extend
this rationale, inactive people are currently not added when posting. It
therefore makes sense to keep this behavior coherent through the mail stack.
Task-3046371 (Mail: Better Language Support in Composer)
Part-of: odoo/odoo#113522