I don't see this as killing anything, honestly. I see it as a way for the staff as a whole to have an idea on how to handle large/obscure words. Personally, I love the use of large words as long as they are used correctly. I don't mind looking something up. In fact, I love it when people make me look a word up because I like expanding my vocabulary.
However, if a word is misused, it can be jarring, but to me, it means that a person might not have thought the word through before choosing it. However, that opinion excludes non-native English speakers, because there is much nuance and subtlety in how words are used in English. I have heard it said by non-native speakers and by English teachers that English is the hardest language in the world to learn. I can agree with that.
I see the potential policy not as something that will totally kill the use of obscure words. I -do- see it as killing the "I used this word and was rejected, but a week later, I saw a PC with the same word and that's not fair!" problem. Again, if you are going to use an obscure word, more power to you, I think that's awesome. However, PLEASE use it correctly, so that when we look it up, we don't get there and go "She's doing what?! That shouldn't be possible!"