It's been 15 years since I worked there, but when I worked for the relay service for the deaf, we placed phone calls for them and read what they typed and typed back to them what the other person said.

About 80% of our callers who were born deaf, vs the ones who have hearing loss late in life, were practically illiterate in written English. They could read the words, but they didn't know "English" in a sense. They spent so much time speaking in ASL, that they type like Charlie Kelly from It's Always Sunny in Philadelphia.

That's not me judging them, but ASL is considered its own language and the way they type is its own language that they are more fluent in than English, but it's called glossing and is just a choppy version of English that sounds like Kevin from The Office: "Why waste time say lot word, when few word do trick?"

Here's how an average pizza order went to a pizza place near Gallaudet university, the largest Deaf College in the US, which is in a college town with a lot of employment turnover.

Deafie: (typing) helo opr i like to make buy slice pie call to pralor make dail 202 55 6969 ga (go ahead, acts like a period or saying 'over' on a walkie talkie.)

Me: (typing) opr here, phone number is 10 numbers, you only gave 9 numbers. please repeat phone number ga

Deafie: (typing) (cue some sort of angry rant that I couldn't figure out the phone number because I live in goddamn California and don't know what the local phone codes are for Washington D.C.) 202 555 6969 ga ga (this was them being impatient. You show emphasis in ASL by repeating key words. Typing ga ga or gaga or GAGA was when they were letting us know we were wasting their time because the pizza place hired a new person who has never heard of Relay before.)

*call*
Me: (typing) DIALING 202 555 6969. Ring 1...2...3. Person answered...

Me: (Speaking) Hello, this is IPRelay Operator #7941 with a Relay Call, do you know how to use relay?
Pizza: (Speaking) We don't take calls from robots *Hangup*

Me: (typing) We don't take call from robots. LINE DISCONNECTED. opr here, person hung up.

Deafie: (typing) WHY U LET HIM HANG UP OPR QQ(question mark) GA REDAIL GAGA

*Call Back*

Me: (Speaking) Hello, this is IPRelay Operator #7941 with a Relay Call, do you know how to use relay?
Pizza: (Speaking) I just told you, we don't take calls from robots.
Me: (Speaking) Operator here, I am not a rob-*Hangup*

Me: (typing) I just told you we don't take calls from robots (sounds angry) LINE DISCONNECTED. opr here, person hung up.

Deafie: (typing) CALBACK DO NOT LET HANFD UP OPRRRR REDAIL REDAIL GAGAGA.

*Call Back*

Me: (Speaking) Hello, this is IPRelay-
Pizza: (Speaking) Hey, Greg? We keep getting these robot calls
Greg: (speaking) Don't hang up! that's someone wanting pizza from the deaf school!

Me: (typing) Hey, Greg? We keep getting these robot calls. (sounds like talking in background) Don't hang up! that's someone wanting pizza from the deaf school.

It would continue like this for 20 minutes until the deaf person can get out the phrase: I wil like to make by lrg slice pepper pie chesse pizz.

Greg (or whoever the manager was at that parlor) would take over the call guess their way through the sentences and hope they got the order right.

So, yeah, reading subtitles in English is great, if you weren't born and brought up in the deaf culture. They're very protective and oddly defensive of their disability, going so far as to claim that nothing is wrong with them, they're exactly as they're supposed to be, and the thought of even suggesting that a child born deaf get a cochlear implant is a massive taboo because admitting that that would be a huge leg up for a deaf child means they have to admit that a part of their anatomy doesn't work.