The intention of this coding style guide is to provide a minimum number of rules to make code more readable, and also to highlight who doesn't respect the project enough to follow the style guide. Rules should be chosen with care, if too many rules accumulate it's not fair to ask people to follow them.
You may add to these guidelines by following the C4 protocol as usual. If there's a problem that frequently occurs and the simplest solution is to add a new style to these guidelines, then do it.