My interpretation of the structure of this site is that proper critique is desirable in the critique-based forums, whereas 'Not for Critique' is for photos whose owners aren't seeking critique. Whether or not a forum for "nice post" and other simple expressions along the lines of a Facebook-style 'like' is wanted around here, I cannot say.
Sometimes there just isn't much you can say about a photo because it's of a certain standard, or cannot be easily picked apart.
Perhaps rather than "nice image", such comments should explain why
the commentator thinks the image is nice. A comment like "I like the cascading water on that rock" at least provides some insight into what makes the image work for that person, and is more useful than "nice image" alone.
Personally, I like to know what it is about my images that people like.
I completely agree. How to cater for that in a useful, meaningful way is not so clear in my mind.
On the other hand, forcing meaningful comments if the person isn't comfortable or able to make them, may stifle feedback altogether.
Time will tell, and maybe that's why Rick has placed a specific time limit on the "nice image" embargo.