History
This tries to explain why some design decisions were taken during this project development.
The script translation-tool.pl considers converting UTF-8 files to
ASCII, but does do that in a improper way using regular expressions.
This might be due the history of Java Unicode support.
In the past releases of Java, there were CLI like native2ascii, but it seems it's usage was deprecated in newer versions of Java (and OpenJDK).
See also https://bugs.openjdk.java.net/browse/JDK-8074431 explaining the subject.
On the other hand, it seems to that Jenkins should be able to support reading those properties files in UTF-8 by default nowadays, but that isn't decided so far.