Am I sinful for not indicating to a worshipper the necessity of straightening the rows, and does that affect the validity of the prayer?

"Straightening the rows is recommended, not obligatory, according to the majority of scholars. Therefore, there is no sin in not alerting someone who fails to straighten the row, and the prayer is not invalidated by it. Alerting a worshiper next to one to straighten the row during prayer is permissible because it is a movement for the benefit of the prayer. No scholar has stated that alerting during prayer is obligatory. Even those who hold that straightening the rows is obligatory do not believe that the prayer of one who does not straighten them is invalid. Thus, your prayer is valid in all cases, and you do not incur sin by not alerting."