Regina:
What if the story does not appeal to you or you find to extreme or unbelievable. I feel it is best to let it alone.
Well, my belief is that many authors appreciate constructive criticism--I certainly do, especially if it presents me with perceptions of characterizations and/or plot elements that differ from my own.
Outside of Challenge entries, posted stories are rather quickly described in terms of plotline (via a short synopsis), gender pairings involved in its spanking(s), general ages (adult, teenager or child) of the characters involved in the spanking action, implement(s) employed and basic type/setting.
So if a reader desires to avoid F/F pairings, or child-spanking, or fanfiction (these are simply random examples), he/she should be able to do so. If there are already comments posted to the story, reading those could also help him/her figure out if he/she would enjoy reading it. Of course, the "Latest Additions" may lack all of these descriptors, because they haven't yet been validated, so a reader risks 'opening' a story he/she might not care for in that case.
If a reader is going to 'fairly' vote on Challenge entries, in other words on all of them, then he/she will likely come across a few that don't match his/her personal preferences--but I'd venture that he/she should still be able to find something to comment on for each story...

--C.K.