I have seen underscores and earmuffs (like
*good*) frequently used in conversations among programmers. All I know is that underscores are used to denote private variables or methods in languages like C, Python etc. and earmuffs are the preferred way of indicating that something is a global variable.
Do these have any other punctuational meaning when they are used outside code, in mailing lists etc? Does the highlighted word have any hidden meaning or expression added to it? Or, are they just like air quotes?