I noticed that there is people writing words between underscores, such as in the LKML mailing list where Linus Torvalds used to use the following pattern in his message: _hope_, _names_, _I_, _one_ ..
That’s not the first time since I have seen the usage, but I wondered the same thing after having found many other people using this form of expression ..
What this kind of formatting is called and when it can be used? Is the usage specific to mailing lists, intended for italic formatting?
Underscores used this way are mimicking Markdown or actually meant to be Markdown. In Markdown, underscores are put around text to create emphasis, or italics. Markdown interpreters will display the text in italics. Markdown is used in this forum, in this answer to create this emphasized text which I typed with underscores around the word “emphasized”.
It’s also called “snake casing” when used to string words together to create identifiers, but given the usage in the link provided it is meant to indicate emphasis in a manner that all developers who would be writing code would recognize: Markdown.