This subject keeps cropping up for patients with PN.

First of all regarding blood levels:

I don't think the medical community can interpret these except for very low ones. The reason is that lab ranges are determined from a statistical comparison of so called normal people who have their blood drawn (who have no pathology that is known at the time). Higher than those ranges would be found in anyone who takes any supplements. For example for B12, people taking a supplement often report out of range values, 1000-2000, when 800 is typically the upper cut off. These high values of B12 only show that it is being absorbed into the body as needed. The tests for B6 are most accurate in the very low ranges, and were initially designed to discover patients suffering from drug induced low B6--- some drugs cause this, like INH which is used to treat tuberculosis.

Pyridoxine has the confusing issue of causing neuropathic symptoms in very high doses, and when deficient, so this clouds the interpretation of blood values also. We are finding --as per the study I quoted earlier in this thread--- that autistic children present with high blood levels --higher than expected--- when there are NO supplements being used. This reflects a genetic error of metabolism of some sort, which has not been explained as yet. But in the face of these results, doctors for autistic children give MORE B6, and it helps.

The only documented studies I have seen on PubMed involve giving GRAMS (1-3 grams) of B6 which were seen to cause neuropathic toxic symptoms. The actual number of people who have been reported to have toxicity from B6 is very small.
This became evident back in the days that B6 was used in very high amounts of 500mg a day or more for treating PMS in women.

Why B6 is building up in some people, is still unknown. Why it is not excreted as a water soluble vitamin is also unknown. But we do know that B6 as pyridoxal is stored for short periods of time in muscle tissue to aid in metabolism and creation of energy. There is B6 in the food you eat. Mostly from meat.
Some fortified cereals contain about 2mg of B6 (Total for example) per serving, and some grains like wheat.

I don't think at this time there is an answer to your question. I could not find any explanation for a small daily intake of B6 to cause your problems. The only way for you to find out what is going on is to stop all B6, stop eating fortified foods, and cut back on meat for a while --6mons or longer-- and see what happens. If you have no intake of B6 you should not have high blood levels. If your levels go down and you still have neuropathic symptoms, then the B6 is not your culprit. All the studies show that ELEVATED B6 neuropathy is reversible, and not permanent.

The medical community is finding that genetic errors of metabolism in humans occur, and they may account for age acquired chronic diseases.

There are people born with a condition called B6 dependency.
These individuals typically have seizures beginning in infancy, and require huge amounts of B6 to stop them. They take doses that are enormous, and they do not develop neuropathy. But they are also rare, and I saw a quote once that only about 100 people have been identified with this disorder.
http://emedicine.medscape.com/article/985667-overview

People may not convert pyridoxine to pyridoxal if they are low in riboflavin-- B2.

Progressing neuropathy can have many causes. Autoimmune, gluten intolerance, hereditary Charcot Marie Tooth genetic errors, insulin resistance/diabetes, thyroid disease, certain drugs like statins and fluoroquinolone antibiotics, and some chronic exposure to toxins in the environment.