Personally I don't like forced commenting one bit. I will generally score a story or poem when I read it because I want to, but that doesn't mean that it actually moves me to say anything. Often times the comments already there sum up what I think or feel about the piece or perhaps I just don't want to comment, have nothing to say that will add or detract. But if I go to leave a score and the forced comment box comes up, I'm more inclined to just navigate away, sorry.
I can see merit in forced commenting for scores of say, 3 and below (certainly when low scores can be a "two-fingers" to a writer that someone doesn't like (the 'political' ones - I hate that and we've all seen it happen) but to be honest, the verifying process should already have ensured that stories don't really fall below that level anyway. I mean, if the spelling, grammar, punctuation or whatever are that bad, then it should not have been approved and posted in the first place.
We all love to get good scores, but as some of the posters above have said, it's all subjective anyway. Some people just score everything with a five, some may rarely feel that any piece merits a five - so a four from them might be equivalent to a five from someone else and while comments are important in letting us as writers know what people like to see or don't like to see, it's just their opinion.
Often I will comment simply to let the writer know that I have been to view their story and, in leaving my comment, I let my other friends know that I have read the piece (sometimes piquing their interest to read it too, hence promoting a story or poem that I liked)
It's also nice to get comments from friends or writers that you admire, it can make you feel good about your work and again perhaps prompt some of their friends and followers to view and score your work, but the key word is "nice" not "necessary".
This is a site for amateur and professional writers alike, a chance to express ourselves, explore things that we might not get the chance to do in real life, to work on our writing style or, as a reader, view a huge spectrum of sex, arousal, love, lust, fetish etc etc, but also to have our work seen by a huge variety of people, so, when I get a score or a comment on some of my work, I feel thankful that someone has chosen to go to the bother of doing that. I don't want to get votes and comments because they have been 'forced' to do it.
We'd get dressed up all nice and pretty, go out, have a few drinks, get very very drunk and giggle rather a lot...
Oooh, move over and make some space for me!