What is the server IP in database trigger definitions?
Thanks to comments by Demerit, my confusion arises from the fact that our MySQL server and web server (with core CiviCRM files) are separate. The 173.236.128.0/255.255.128.0 mask matches our web server and so that definer field in the trigger just indicates the server from which the triggerRebuild command was executed. There was nothing wrong with our website operation. I just didn't understand the source of that IP, thinking it should match the IP of the MySQL server, which is wholly different. A good argument for a true VPS where you have full control of both Apache and MySQL on the same server.