We purists do not use "c" for "see" and "4" for "for" in text messaging. We certainly do not use "wud" for "would." And the list goes on. How many of us put in all punctuation in texting? Well, of course we do. How inconvenient that it is on a separate screen.
When it comes to putting a text message into the transcript, the question arises as to whether or not to use the symbols and "abbreviations." There is no "rule" for this. And if you do not have the text itself to look at, there is no question that you will use regular English.
My advice is this: If the actual words are in question in the testimony, by all means, use the symbols and the words that are in the text. Otherwise, transcribe the text in normal English.
Happy punctuating!
Margie