Just spent a while trying to figure out what was causing me to get 2 EOL per write. When I wire an EOL constant to a Format into file on windows, it reads the CR LF and converts it to CR CR LF. Reading up on the help
"This function converts new lines, or \n, in the format string into the platform-specific end-of-line character, for example, CR/LF on Windows, CR on Mac OS X, and LF on Linux. If you do not want to convert new lines into the end-of-line character, use the Format Into String function and wire the resulting string output to the text input of the Write to Text File function. Then right-click the Write to Text File function and remove the checkmark next to the Convert EOL shortcut menu item."
So even if you have the os specific eol it still can do some converting!