Hello Edwin,
The API Mendix exposes does not offer that, nor is there any function to edit commit messages in the Modeler itself.
Tortoise can allow it but only if the repository is set to allow message edits (As you’ve said), you can read a bit into some solutions here, perhaps the technical contact user will be able to retroactively change the log settings
Obviously the repository is created by Mendix so any question on the configuration would have to be addressed to them in a ticket.
Hope this helps