Consistency in a project is crucial both for the source code itself and the documentation. People who work on the project are habituated to use the standards they used for years, and would be lost in front of a piece of code or a part of a documentation which, in your opinion, is better, but which has nothing to do with the remaining codebase or documentation.
Also, be aware that it's not because you think that something is bad, it means that it is. Referring to Code complete doesn't change anything. What you may criticize might have its source in some elements related to the project, and while Code complete says it's bad, anyone who worked on the project for years would agree that in this specific case, it's the only choice.
If you want to improve the documentation of an existent open source project, gather some feedback from other people who participate to this project, and if you see that everyone agrees that the actual documentation is too bad, then well, you may want to rewrite it from scratch, following the best practices and keeping the consistency at the same time.