Don't know if it's been mentioned before, but if you copy a piece of text from somewhere in your message, and paste it somewhere else in that same message, it doesn't copy the formatting, things like Bold and Italic etc.

For example, if I were to copy that line I just wrote, and then paste it somewhere else in this message, it will copy the words, but it replaces the formatting with markup rather than show what the markup is supposed to be setting.