That is hilarious.
I don't think it's hilarious, nor ironic (as the OP mentioned.)
If an instructor speaks a lot about the need to restrain talking, then that means the instructor thinks the students talk too much. (...or, less likely, it means that the instructor feels the topic is so important that it bears repeating even if everyone present is already not talking too much.)
On the other hand, *students* on the mat who are telling other students they talk too much... that is certainly ironic and funny. So we could ask: Does the talks-about-silence instructor talk too much when they are on the mat with their teacher? That would be a good gauge of the quality of that particular instructor.