For me, no one symptom of low B12 should be the end all on the subject.
For me, ridges on my nails were especially wide and raised and I had no moons on most of my fingernails when I was suicidal and depressed and had a lot of peripheral neuropathy pain as well as extreme pain in the bones of my legs.
I have observed that as I had B12 replacement, all of my symptoms reduced.
Therefore, to me, the way that people's fingernails look may be a clue to their need for B12.
Hopefully it's been a helpful clue for many.
I'm always delighted to visit a new forum and see people talking about how because of ridges on their fingernails they went out and got B12... I sure wish I'd been clearer earlier on about how Methylcobalamin is the best form to get.
Still, some B12 is probably better than none, only if there are severe symptoms of low B12, then a tiny bit won't do much good and I'm afraid the person will give up for lack of appreciable results.