Most people enjoy commemorating a special moment with a photo, and being able to easily relive that memory a few years later. Smart digital technology makes this cheap and easy. Sure, having the camera out all the time is compulsive. Going through and manually editing, tagging and deleting photos is compulsive too. Most people do neither, but they still want to keep their photo memories safe.
It could include that but doesn't require it.
Analogy would be crazy cat lady doesn't have 100 of anything with fin fur or feathers, she's got 100 cats. That doesn't mean crazy home zoo guy in florida with 10 aligators and a tiger isn't any more or less whackier if its messing up their lives just as much.
Also the criteria is not the useful or not, its the impact on life and human happiness. I have a full digital set of all star trek episodes from all TV series... ever... if I lost them I would be pissed for awhile, but I wouldn't cry freak out drive around looking for backups in a panic and get in way over my head technically (which for me would be way more extreme than the guy in the original story). Kinda like some folks without an alcohol problem can drink a couple beers without negatively impacting their lives, but a pretty good working definition of a guy with an alcohol problem is he drinks the same beers and his life totally falls off the rails... the problem is the impact on life not specific ethanol molecules.
Everyone likes your second paragraph. The problem is for some/most people its exclusively a positive activity, and for others the positive comes with epic legendary freakout mode. The problem is the epic freakout mode not liking pix or putting in a reasonable non life impacting effort to curate their pixs.
Toward those with a problem, it is possible to feel some empathy as their illness negatively impacts their lives while still recognizing the illness as an objective fact. Your analysis that those not showing some minimal level of empathy are mean spirited and stupid sounds more or less correct to me although its a matter of degree which makes it messily analog and complicated.
As for commentary about lost memories and such, in the long run we're all lost. Live your life to live, not to be documented and preserved. You're a person not a wikipedia article. I don't think you'd like most eastern philosophical outlooks on life; but we don't have to all agree with each other, merely be civil enough in our near direct opposition. Historically humans have done worse.
I would disagree with the ignorant, useless commentary in that most people know (of) someone with a hoarding problem and here on HN we know all about complicated technical rituals. As for the useless thats hard to parse, there seems little point in referencing a hoarding support URL in a locale where we all pretty much know how to google. And people who are sick usually already know so mentioning it isn't helping, as you correctly mention.
Overall a mixed bag, 7.0/10.0 as a comment about half the wide ranging comments were good and/or half good, some not so good. Well written from a literary standpoint although some logical argument issues behind the first glance.
On a broader scale I think its interesting to consider hoarding in the digital age; not seen much on that. Most of the diagnostic criteria from meatspace should transition pretty smoothly into tech; is the behavior negatively impacting the victim, and so on.
I don't think the cure for digital hoarding will be bigger storage or more outlandish technical schemes; I suspect a lot of people agree with me; this is probably the root of the "backlash" rather than some inherent hatred of victims. The dude in the article is doing the exact wrong thing to fix his fundamental problem with outlook on life, therefore intense backlash. I wish him well, even if I think he's going in the exact wrong direction to actually fix the problem.