This topic has been bothering me for a while.
Word choice can enhance a story, but it can also distract.
Sometimes authors use really awesome words like "verisimilitude" or "imbues." These words get across the meaning much better than other words or phrases could do.
As a word geek, I know these words, and get excited when I see them used.
As a beta, though, I have to stop and really think about the word. Would the audience understand it? Could they pick up the definition from contextual clues? Should this word be replaced with more common word? Does the word distract from the story?
I also have to keep the character in mind. Would they use this word? Would they even know this word? Does this word fit the scene?
And honestly, I'm not sure what to do in every situation. A lot of the authors I beta for use amazing words, and a lot of the time I ask them what they think they should do. If the story was just for me, I'd leave every larger word I see. Because it's not just for me, though, I really have to guess about the general knowledge of the reader. And that's hard.
I guess this lesson to take from this is that sometimes betaing isn't black or white. Sometimes you have to talk it out with the author. And sometimes you have to change really awesome words.
I would also like to pose this question to you: Would you like an author leave in larger words, and just assumes the audience understands/can figure it out, or would you rather have the author (and I hate this phrase, but I can't think of a better one) "dumb it down?"