While I highly support being polite when commenting, I also highly support being truthful.
By sugarcoating a comment you're making it superficially acceptable, attractive or excessively sentimental. Where any mistakes or inconsistencies are ignored. In some situations, sugarcoating could be seen as lying to spare someone's feelings.
Although my nickname may be Sweet, I'm not the type of person who will be so sweet that I'll hide the truth or give out a comment that ignores quality.
So let this stamp show that if you want an honest critique (be it on your writing or art), I'll be respectful but give it to you straight.