10k IU/day exceeds the Tolerable Upper Intake as determined by the US's National Academy of Medicine, the European Food Safety Authority, and similar organizations. Medical doctor Deva Boone posted a report of toxicity at half that dose:

https://www.devaboone.com/post/vitamin-d-part-2-shannon-s-st...

This post and related posts about vitamin D were discussed on HN. See:

https://news.ycombinator.com/from?site=devaboone.com

I know, but that's in error:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541280/#:~:tex....

Doctors correcting vitamin D levels are finding 10k IU is a good starter dose and that is often insufficient to arrive at optimal levels.

Here's another report of toxicity at a similar dose:

https://jeffchen.dev/posts/Vitamin-D-And-Heart-Palpitations/

Dr Boone posted on HN, and claimed that vitamin K2 would not counteract high dose vitamin D:

https://news.ycombinator.com/item?id=24262492

I am not aware of any randomized controlled trial of vitamin K2 for protection against vitamin D toxicity.

Really the only way to know the correct dose for any individual is to conduct occasional blood tests and dynamically adjust up or down. There as so many factors including diet, body composition, sunlight exposure, genetics, etc. One individual might need a daily dose several times higher than another.

In your article the person was taking this dose for 5 years, and probably without vitamin k2 and developed hypercalcemia.