what is 'duckspeak' ?

A reference to George Orwell's "Nineteen Eighty-Four", where it means "to speak without thinking" / "to quack like a duck".

Calling something (...)-speak is often a reference to the novel (and has a negative connotation), like newspeak or oldspeak.

what does '/nt' mean

"No text" (in the body of the message, the subject line is the actual content of the message).