raph: I know it's likely been said many times before, but folks along the lines of bytesplit and OpenSourceJapsEye (if I remember correctly) are a useful metric in themselves -- few people want to try for negative attention someplace that isn't a fairly strong positive overall.
In terms of useful feature suggestions, may I suggest a "subscribe/ignore" feature such as found on Freshmeat? I think it would be a good way for users to keep track of their favourite diarists, while not being annoyed by those whose opinions they would rather not see.
I envision a new box on the main page, being "subscribed diaries" or the like -- sort of an elective recentlog. I know it will be one more step towards front-page clutter, but I know I would find it fabulously useful, and can only assume that others might, as well.
Of course, I'll be willing to work on a patch, if that's your preferred form of new feature submissions.