If it's on the archive, the short blurb plus the size of the story are usually good enough to figure out whether a story will be an angsty drama or a short comedy.
I would never nominate a story I hadn't read no matter how much I love the author. Even if a story isn't a clunker, any author is capable of putting out a so-so story that I would perhaps read once or twice and then never again. Or perhaps an author is very good at a particular type of story and isn't quite as good at others, e.g. good at angsty but not so good at comedy.
Another possibility is that an author may end a story in a controversial manner in an otherwise excellent story. I'll apologize ahead of time to Lynn for singling one of her stories out, but her excellent story, The Butterfly Legacy, comes to mind. While I loved the whole story and thought it was quite appropriate for one of the major characters to die, others thought that development ruined the story as the FDK threads spawned quite a discussion.
In any case, by not reading a story, you're basically nominating blind.
P.S. I had an underhanded reason for bringing up BL. I just had to nag for the Lost Chapters.
