I ran across a flagged answer ([it is deleted now, so you need enough rep to see it](https://stackoverflow.com/a/14583065/335858)) which is basically a link to a blog post. The link explains precisely how to do what's asked in the question, so I marked the flag "invalid". Moderator disagreed, and deleted the answer.

I understand that link-only answers are frowned upon on Stack Overflow sites, and for very good reasons. However, I did not think that they are automatically considered a valid target for "not an answer" flag -- regardless of how helpful the link is. The moderator who deleted the answer obviously disagrees with me. 

1. Why did he disagree?
2. Should I even bother investigating the helpfulness of the link while reviewing these kinds of flags in the future?