Everything (minimal example and screenshots) is in the git repository: https://github.com/renn0xtek9/KDE_Highlighting_horror.git
The markdown file contains bold here on mageia v7 x86-64. Does it happen in a new user?
Please check bug 383665 comment #1.
Thanks Christoph Fleck that was it
*** This bug has been marked as a duplicate of bug 383665 ***