Every uncoated pill that has a curved surface can be split by placing it on a hard surface and pressing down on opposite sides with your thumbs. The split is more accurate if it is pre-scored -- place the scoring/groove face up during the split. But even without the groove, it is rarely worse than a 55:45 split in my experience. And no, I have no idea why this story is on HN.
Children sometimes get prescribed medication that a pharmacy might only stock in an adult dose pill. If the pills are small, a pill cutter is a lot safer than splitting them with a knife.
Another application would be if a doctor recommends reducing the dose, but you still have a lot of the originally prescribed pills.
People who have to regularly take half a pill sometimes struggle with breaking the pill into clean halves, or don't like having to use a kitchen knife or whatever and clean it later.
Not every medication is manufactured in the precise doses required. To get to the right amount, a few common doses will be produced with score marks to allow easy(ish) division for a smaller amount. For example, one of my family members has needed a half-pill of thyroid medicine. Something like a 75mcg pill split in half to make it 37.5mcg.
Another application would be if a doctor recommends reducing the dose, but you still have a lot of the originally prescribed pills.
In fact the opposite happens here, you end up with instructions like "Take ten", each of which has to be individually popped out of a blister pack.
https://news.ycombinator.com/user?id=bookofjoe
EDIT: Yeah, obviously there are dozens at 3 bucks on temu.