CommonMark specifies that, while asterisk * can establish within-token emphasis, underscore _ cannot.

Expected Behavior

Input

underscore_containing_token

should not have any emphasis, even though

asterisk*containing*token

emphasizes containing.

Actual Behavior

underscore_containing_token

emphasizes containing the same as with asterisks.

Software Versions

markdown-mode version 2.4-dev (installed via MELPA)
GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.21) of 2017-09-22, modified by Debian
Ubuntu 18.04.4 LTS