What is the ruling on the innovated method in Islamic law that involves daily attendance logging in forums by sending blessings upon the Prophet, peace and blessings be upon him, and the member repeatedly replying with this formula due to frequent logins?

This is a good method, and there is no objection to it. Rather, it involves inventing a means that helps people do good and reminds them of what they should do regarding sending prayers and peace upon the Messenger of Allah, may Allah bless him and grant him peace. It also contains a kind of cooperation in good deeds. The person entering should be reminded to anticipate the reward for this action of theirs.