I'm just curious as to how you know for absolutely certain that this person isn't Hoh or doesn't have a severe auditory processing disorder?
Have they explicitly told you "I can hear just fine, but I like to pretend I'm deaf, so I fake not hearing things" ...
I have read about many perfectly sane people who are Hoh or have severe CAPD/APD who honestly feel they'd be more comfortable if they lost most/all of their hearing ... to be clear, this is different than being a "deaf wannabee" because some people who are HOH or have CAP/APD find that their hearing actaully becomes a hindrance because they're not able to understand anything but are bombarded by noise that is constant, confusing - sometimes loud, sometimes painful. For these people the idea of losing more hearing isn't "insane" - it's actaully quiet rational - an end of the auditory chaos (which is tiring, and distracting!) that gets in the way of them being able to focus on other forms of communication including ASL, speechreading, cueing etc
I've also read cases of some "deaf wannabees" (very very few of whom want to learn ASL,I guess they figure they'll just be natural perfect speech-readers or something ??) - and as Jillio mentioned, these people have a mental illness, similar to people who want to be blind, or those who want to be amputees and either "hide" their limbs or actaully intentionally create "horrific accidents" which not only amputates the limb/part thereof but also damages the amputates section preventing anyone from being able to reattach it - even against the patient's will.
These people really need to be treated with medication and therapy ... the problem is that most people effected by this mental illness don't understand that they're actaully ill
due to the type of hearing loss I have, in addition to a mild, APD, as well as other medical conditions that cause the amount of hearing I do have to fluctuate - I've been accused a LOT of being some sort of "Hoh wannabee" - by which I mean, people are absolutely certain that my hearing loss isn't as "bad" as I say it is (I'm profoundly +120db deaf on my right, mild.mod flux on the left).
Even my family , who's SEEN my audiograms, hearing aid etc , occasionally accuses me of "selective hearing" (depending on what side they stand on, how much background noise there is, how I'm physically feeling etc - I may hear almost everything - or almost nothing ... frustrating for me, frustrating for them too!
Because of my experience with being accused of somehow "faking" how much I hear - I'm always VERY VERY careful about doing them same about anyone else... I've learned the hard way that I have days where I'm "almost hearing", but just as many , if not more days when I'm "almost bi-laterally deaf"...I can only imagine what that must seem like to people looking at me "from outside" ....