[Lewton]

Full paragraph:

"People will so often put up photos on social media of obliterated helmets and say, “Holy crap, look at my helmet! It saved my life!” But helmets are not supposed to shatter. When a helmet protects your head from a serious injury, the styrofoam inside will be compressed and stay that way. Most of the pictures I’ve seen are of helmets that have broken apart. It’s likely that the helmet did not protect someone from a severe injury."

[kolektiv]

In which case yes, just a very misinformed original author. Shattering, cracking, etc. are all known, planned features of a helmet impact - anything which can absorb energy in the helmet and not the head is a good thing (with some obvious caveats of course).

[moopling]

Depends, depends... Fracturing of a flaw requires much less energy than plastic deformation. So it is really a question of whether it deformed first and then cracked, or fractured early. In the latter case, possibly caused by a flaw or very sharp impact, not much energy would be absorbed at all!