A search of PubMed articles using keywords "booger," "muchoid," "nasal discharges," and even "rhinotillexis" yields absolutely zero results that could support the cited blog post.
Reputable medical research does however caution against nose picking. In an article in the Journal of the National Medical Association by Albert Seltzer, who writes that:
The physician is frequently concerned with the harmful effects of meddling with the nose. Into the office of the general practitioner, the pediatrician, and the nose and throat specialist come literally countless patients with disease and injury to the delicate tissues of the nose resulting from injudicious probing with the tip of the fingernail.
Even more seriously, a study in the 1992 issue of Psychological Medicine concludes that "Later-onset AD [Alzheimers Disease] was found to be positively associated with starvation/malnutrition and with nose-picking."
In short, Dr. Bischinger (mentioned in the linked article) has provided us with zero evidence for his assertions. He has not published his findings in a peer review journal, nor do other studies support his conclusions. The eating part is therefore dubious.
By contrast the dangers of nose-picking are well-documented, and must outweigh any supposed gastrointestinal benefits of ingesting mucus.†
†Please note that this answer does not constitute medical advice. It is only meant to summarize published research related to the topic and limited the cited sources. Consult your physician about what these results may mean for your health.