The change "Punctuation to Text" checkbox toggles the keyboard
punctuation marks to text in accordance with NTS MPG-SENDING
ON VOICE.
http://www.arrl.org/files/file/Public%20Service/MPG204A.pdf
The documents states: "Remember that
punctuation, other than X for period, is always written out as a word
group and may be spelled if necessary.”
Original form credits to OE3VRW, Wolfgang Ruthner