After conferring with the committee and reaching out to Duxbury, the closest thing to a comment placed in the text would follow the tilde in the [idle~] code. Since no spaces are allowed within codes, you would have to separate each word with an underscore. For example, if you wanted your comment to read, "text to be deleted," then the code would be entered as [idle~text_to_be_deleted].
Also, there does not seem to be a limit as to the length of the text following the idle code. Therefore, you could write your code with the words unspaced and using title case, as in [idle~25Lines38CellsInterpointEmbossBraillo].
When the DXP is translated to a DXB, the text within the code does not appear within the braille document. You will have to include spacing around the code, otherwise your braille text will run together since the translator ignores the [idle] command.