Bhikkhu Pesala wrote:preaching to deaf ears is a waste of time and effort.
I know this probably wasn't the intended meaning of your phrasing, and it is unrelated to the topic of this thread, but I still would like to share a couple of things.
A few years ago, when I came out of someone's apartment, I had the fortune (maybe not from a Theravadin perspective) of running into a Tibetan monk who walked by. I bowed to him. He seemed happily surprised, so he bowed back. He then started to say something... so, I had to let him know that I was deaf.
When I said this... he acknowledged it very little, and then just walked away. He looked straight ahead and didn't even look back.
I think it's possible he's probably heard an advice similar to yours, and took it a bit too literally. I don't think that this is something limited to the Tibetan tradition (and I'm pretty sure that not all of their monks would behave in the same way)... so, I still can imagine a similar thing also happening with a Theravada monk. Why? It's my impression that the traditionally Buddhist countries have some backwards ideas about deaf people.
A deaf friend once shared with me that he couldn't register for a 10-day vipassana retreat because he was deaf.
He was told that the "auditory feedback was integral to the practice." It seemed strange to me... especially considering that he was a good lipreader, and is able to speak well. (Unlike me.) I think that this was just a reflection of the general attitude in the traditional Buddhism, towards a deaf person. (Or to what we're actually capable of doing... to give this a bit more charitable interpretation).
To keep the topic of this thread: I think it is definitely the job of monastics to give the blessings, in the form of Dhamma, whether it is to a deaf person or not.