Currently it is impossible to use italic in the middle of words, because the import plugin will render underscores in the middle of words as underscores instead of turning them into italic (As it should, see commonmark specs and github specs).
For example exporting "testitalicword" and then importing it back would result in test_italic_word.
Possible fix
I tried fixing it by changing the italic from underscore to asterisk inthe draft-js-export-markdown plugin and for me it seemed to fix the issue.
In source