Steps to reproduce
1) Run a job that will archive a text file with UTF8 text
2) On the job page under build artifacts view that file

In my case on all major browsers on multiple OS's on different machines I get this when viewing the file through Jenkins:

â ⠓⠑⠊⠣⠞⠀â ⠁⠃⠧⠀â ⠎⠑⠁⠀â ⠇⠑⠧⠑⠇

instead of this (UTF8 braille) when viewing the file directly from the filesystem in a text editor

⠠⠓⠑⠊⠣⠞⠀⠠⠁⠃⠧⠀⠠⠎⠑⠁⠀⠠⠇⠑⠧⠑⠇