Ask HN: Why is my comment [dead]?

I have submitted few URLs in a comment thread and my comment is showing as dead,

Here is the comment,

https://news.ycombinator.com/item?id=6490472

What could be the reason?

You may need to turn on your showdead option to see the comment.

[EDIT: It is not dead anymore. But the question remains, what could be the reason? too many URLs?]