Anyone is welcome to post comments and feedback on threads posted here to help creators improve their work. Even if you don't know how to create content, constructive feedback like, "Maybe try a shorter hair that's a bit more blonde than brown," or "I think the green you've used is a bit too bright," is helpful.
Please stick to constructive feedback only! No, "This sucks," or "I don't like it," type comments. Those do absolutely nothing to help that creator improve. Please be gentle, kind, and offer helpful comments like, "The colouring seems a bit flat - try adding some shading and highlighting," or "Try making the celeb sim's nose a bit narrower, and maybe change the lips to something less shiny."
Also please remember that creators are here because they want to improve their work - posting on a thread that was rejected for not meeting the Creator Guidelines saying "Well I think it's good, I'd download it anyway" or "Eh, just post it on InSIM/the Exchange instead" does not help creators improve their work to get accepted here, and will be removed.
Remember: Creators are people with real feelings and emotions, showing pictures of their works-in-progress wanting help. Try giving a few nice comments about the things you do like, especially if you're posting a long list of things you don't, with suggested changes. This helps creators learn what to focus on that's good about their projects, while improving the things that need fixing.