This is the comment:
First of all you didn't follow their advice - they specifically said a musical artist, of which Bieber is neither.
Why is this flag declined?
The content in question is not there because it belongs to a mod. It is there because it is highly upvoted.
I think I am the single greatest remover of comments on Sec.SE (almost 5000 comments deleted or moved to chat) so I am generally pretty harsh on 'noise' in comments, and my main criteria for removal are pretty much as follows:
In initial stages of a post, I'll remove because of option 1. If a post gets busy option 3 comes into play. Option 2 is also looked at, but high numbers of upvotes show that someone likes it. Many someones. So I'll typically leave it.
Later on if I'm cleaning up that post for any reason, it may be cleared out, but if it has high enough votes I may still leave it there.