How to reproduce:
Install Liferay 7.2.1GA2, as an admin user, navigate to Control Panel.
Go to Control Panel / Configuration / System Settings/ CONTENT ANDDATA - Comments
Define the messages so that they contain non ASCII characters, such as the scandinavian characters ä,ö and å.
The messages may be stored, and then they work correctly.
However, once they are stored, they can also be exported to a .config file. Export the configuration, copy the configuration file to another installation (folder <liferay-root>/osgi/configs) , start the liferay service, and check the messages in the Control Panel of other installation. (Or alternatively, use the same server, reset the configuration in Control Panel, stop Liferay, copy the configuration file to the <liferay-root>/osgi/configs folder, and restart the server, go to Control Panel to check the configured messages).
The non-ASCII characteres are corrupt.
The characters should be shown correctly.
If you manually re-encode the configuration files to ISO8859-15, the characters are shown correctly in Control Panel. So it seems the file is generated as UTF-8 and read as ISO8859-1(5).