The post that was quoted here has been removed
One of the fellows I had class with left the whole PhD program after a disagreement with his guiding professor on something that was never actually disclosed to us. It was utterly shocking because I had felt that he got along with the Professor, who was reasonable, though a bit disagreeable.
I also viewed the student as similarly a very reasonable and nice guy.
It kind of boggled me that two people I liked had ended up coming to such an extreme impasse.
There were also times where students fought with one another over administrative issues or even rivalries. I found it to be shocking. I also found that a lot of people had big egos -- it was something that did not bother me so much, because if I let it do so I would be a hypocrite, but it was, nonetheless, shocking and unpleasant at times.