In https://docs.redhat.com/en/documentation/red_hat_openshift_pipelines/1.18/html/pipelines_as_code/managing-pipeline-runs-pac_creating-pipeline-runs-pac#restarting-or-canceling-pipeline-run-using-pipelines-as-code_managing-pipeline-runs-pac , make it clear that all the listed comments can be added in two ways:

• As pull request/merge request commands in, I think, all Git providers (but recheck that with Dev/QE)
• As parts of a commit message on a pushed commit in GitHub and GitLab only