So I sent a plain text document created in TextEdit from my G4 to my Quadra today, only to find the formatting all screwed up when I opened it in SimpleText. I assume this is because Apple has set ...

Type the first line of text into your TextPad program. Press the "Enter" key once to force a single line breaks. Press the "Enter" key twice for double-spacing.

For some silly reason, OS X’s TextEdit app’s default format is rich text. If you prefer plain text, Defaults Write points out that you can easily set that as your default with a Terminal command.