I fully agree with you since I face the same problem with all the participants across all age groups. The moment you initiate a discussion on written communication, all students tune off. Apart from participants, who want to make a career in a function, where competency in written communication has to be excellent, others find it a dull and monotonous exercise.

Punctuation unarguably plays a very critical role in written communication. Give each student a specific designation and tell them they need to write a memo. Tell them the memo needs to be short and precise. Do not go deep into the formats initially. You could also think of examples where the wrong placement of a punctuation mark, the wrong usage of a word, or the wrong structuring of a sentence, can alter the meaning of the message. The best way is to combine written communication with punctuation marks, which will ensure that students really enjoy the task and  automatically get initiated and motivated.