just thinking about jo's dad bill being Deaf and passing his deafness down to jo. but then he dies before she can truly get an understanding of what that means to her. so aged 10 she's left with a patchy fluency in ASL which can do no nothing but deteroriate over time and very little tying her to her cultural heritage (ellen knows ASL and things from bill but she's hearing; it's not the same) and that's why ellen is so protective of jo, because she knows firsthand how dangerous hunting can be, especially for deaf hunters. and then dean turns up, a winchester just like john, and of course she wouldn't want jo to hunt with him - john never learnt ASL, never really found a way to communicate properly with bill while hunting. but she sees the way dean laughs a little blankly at what she says, and reacts a little too late in conversation, and sees that maybe dean is more like jo than he is like john. and so two deaf kids who have grown up in complete isolation from any other deaf people finally find a community in each other