Yeah, this is a debate that rages on...
It's mostly anecdotal. I feel like it gives me more energy and focus, even though I'm not deficient. Don't think it really effects my appetite, although I've never taken it for that purpose and tried to take note of it.
It's been used on ppl with peripheral neuropathies, and various demylenating and neurodegenerative disorders, evidently with sometimes positive results. I don't think it has any inherent toxicity, and I think sometimes the issue of deficiency on blood tests is a red herring; kind of like when the doc tells us our testosterone level of 250 is "normal".
In other words, is scurvy the only indication for Vitamin C intake? Is beri beri the only reason to take B vitamins? So probably, pernicious anemia is not the only indication for B-12.