You mean the tendency to laugh at the person for 'being miserable' when you've played a part in making their life such that anyone would be? I'm puzzled by the weird thing of 'being happy' apparently makes people likeable - it goes against all logic in that people who do what they want and might be unpleasant to others can be very happy and others reward them again. The two often are opposites to each other of 'nice person' vs 'happy'. Then turn it round?
Anyway putting that debate aside, I think the suggestion of the diversity reporting is pretty important because all illness have a mixture of people with whatever propensities and individual characteristics. Finding that the only time ME/CFS is portrayed in a year is as a grumpy internet troll or a faker is rather different given it is a trope (and that term needs to be used, it isn't based in truth and was invented for gain/distraction) pushed by certain factions currently and regularly (cite Fiona Fox and her inaccuracy for one) rather than e.g. an illness well-understood represented in numerous different ways each week.
For that reason switching it to a cancer patient would be very different indeed. And would have made for a deeper and more interesting point of note anyway as people would think of things like 'what happened', 'why' and the individual. They've got tropes they understandably weren't too keen on years ago and have to put up with 'fighter' and all that nonsense rather than being them, great if that's explored in depth, unless it becomes the cliche of every programme.
I horribly suspect she's chosen these illnesses not because of real life evidence, but because of the prior advertising of such tropes meaning she didn't need to unbundle the character but it 'doing the work for her' of 'a miserable troll'. Which says it all about its tropism.
Who'd know there were loads of us picking up the slack for colleagues despite being done in, helping out friends who aren't told of the illness because they are inadvertent bigots, 'hiding in plain sight' whilst our body disintegrates pretty obviously and any of the joyous things others enjoy outside this (like not feeling awful from overexertion as well as collapsed post-work) become impossible yet we still smile, but the public claim they either can't see or it's something else because of this nonsense.
And that if we use the appropriate words to describe the level of bigotry someone just said to our face it is manufactured as if that is anything but 'correct and accurate pulling up of something out of order'. So yes maybe there is some back story they could slide in of a wonderful person who the protagonist is awful to, and when they get told what anyone should say to someone being like that they play victim and pretend they've been hard done by then yes. But the programme isn't that long and doesn't sound nearly sophisticated enough for that to not look rather out of place to pull off. If a producer can be clever enough to work with the actors to get that done then they'd be showing their worth?
