How Honest Should We Be?

I have a question about giving feedback on posts on other member's sites and how honest should we be.

I understand the value in positive feedback It is human nature to be apprehensive about 'putting yourself out there' by submitting a post up for appraisal.

To receive positive feedback is good for the soul and will ensure that next time the member will not be so worried about submitting their work.

Negative feedback, as long as it is constructive, can also be positive as long as it helps. However, when you come across a post where there are spelling mistakes and the content has been plagiarised and in one case, copy and pasted, do we comment on that?

I noticed it because the post was in a different font to others and so out of curiosity I checked. If I was able to determine that a post is not unique then Mr Google will certainly be aware of the duplicate content. Do we comment on that in our feedback? Should we even be concerned about duplicate content?

I read some earlier posts which suggests that Google is not concerned too much with duplicate content unless it is spammy. (is there such a word?) They are more concerned about which page to index for the content created. However, I am sure that content copied from another site will not rank as high as original content. Should we comment on that?

I thought about this situation for longer than I should have the other night and really did not know which way to go. Will I be honest and say that you should consider rewriting your post (s) and carry out a spell check on the content or that the content is great even though it isn't yours....

Has anyone else been faced with this predicament and if so, how did you handle it?

Stephen