Go for it!
You'll also notice that the code uses different styles in different
places (because of different authors). We've not gone through and tidied
stuff up because we're lazy and because there never seems to be a good
time to do it (it causes conflicts with patches people are working on).
If you need to write a style guide, why not use
as a starting point. It's widely used in the Haskell community nowadays (e.g. it's a common recommendation on IRC) and it's based on the coding style of Duncan, Bryan, and Don for the most part.
-- Johan