Defamatory? I don't think so. I could if necessary produce evidence from past threads to support my opinion. I have personally been on the receiving end of a tirade from CC who suggested I was talking cr*p in response to some information I posted which was trying to help out someone else's query. The information I gave was subsequently supported by later posters.
FFF has hit the nail on the head. I have indeed never met CC (although the times I was in the BFC bar recently I did look out for her!), so my opinion is formed from what I read here. My point was that that opinion might prevent that particular individual from getting past the paper sift to discover that she is in fact a nice person. It is that which we should all bear in mind before pressing 'Submit'.