Although the most I people I have managed over has been 2, I found using text files is much better than using comments because people can't be like 'I forgot what comment this and that was in so I couldn't check it'
These are the rights I usually give out;
PHP Code:
r notes/*
rw notes/accountname_*
r notes/documentation/*
r notes/assignments/*
r notes/old/*
r notes/old/*/*
It allows people to leave notes if needed and lets people see what other people are also working on to keep them motivated.
Comments are just too easily forgotten which is a problem. With this it is also easy to back up all the notes if needed without accidently forgetting a few.