Hi @BERIARD Anne 

In ServiceNow, allowing the Change Requester (the Requested By user) to approve the same change request they submitted is generally considered a violation of ITIL best practices.

Allowing requesters to approve their own changes can create a conflict of interest and may enable users to bypass established review processes, authorize unauthorized work, or avoid independent oversight if issues arise after implementation.

For these reasons, auditors and compliance teams commonly require approval workflows to exclude the change requester from the approval chain.

Refer:

https://www.servicenow.com/community/itsm-forum/change-prevent-requester-from-approving/m-p/606308

https://www.servicenow.com/community/itsm-forum/prevent-change-requester-from-approving-their-own-ch...

https://www.servicenow.com/community/guided-learning-itsm/how-to-restrict-agent-as-being-approver/m-...