Today I have been typing on Gmail chat, and by accident I have found out how to type a word in bold. With a bit more of a search, I have also found out how to type in italics, and also strikethrough a word.
Here is the cheat sheet:
Bold: Surround the word with asterisks, e.g. *word* -> word
Italics: Surround the word with underscores, e.g. _word_ -> word
Strikethrough: Surround the word with hyphens, e.g. -word- -> word
If you know more “secret codes”, feel free to leave a comment!