I was trying Markdown in 3.1.0.

Accourding to http://daringfireball.net/projects/markdown/syntax#em it is posiable to use emphasis inside a word.

Qoute:

You can use whichever style you prefer; the lone restriction is that the same character must be used to open and close an emphasis span.

Emphasis can be used in the middle of a word:

un*frigging*believable

My Markdown code:

un*frigging*believable

un_frigging_believable

un***frigging***believable

un__frigging__believable

un___frigging__believable

HTML output:

un*frigging*believable

un_frigging_believable

un*frigging*believable

un_frigging_believable

un_friggingbelievable

*this text is surrounded by literal asterisks*

HTML output should be:

unfriggingbelievable

unfriggingbelievable

unfriggingbelievable

unfriggingbelievable

un_friggingbelievable

*this text is surrounded by literal asterisks*

Environment:
Redmine version 3.1.0.stable.14476
Ruby version 2.2.1-p85 (2015-02-26) [x86_64-linux]
Rails version 4.2.3
Environment production
Database adapter Mysql2
SCM:
Subversion 1.8.8
Git 1.9.1
Filesystem
Redmine plugins:
no plugin installed