Discuss models use relationnal fields. Since [1], the implementation of the `unshift` method changed for `many` fields. The new implementation is incorrect: unshifting several records results in an insertion on the inverse order which differs from the native implementation. This issue broke the loading of older messages in discuss: older messages are inserted with the `unshift` method thus in the inverse order. [1]: https://github.com/odoo/odoo/pull/136539 closes odoo/odoo#140747 Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>