There's a question here about whether or not /c require a community. You might be the only one interested in whatever, or your /c might just not be of interest.
I say this as someone who on other site had a simple /r where I just reposted things I found interesting to my friends, (all 4 of them) who mostly lurked with the occasional upvote.
I think that in creating 'rules' or 'guidelines' like this, we've got to be flexible enough to allow for very, very small communities to exist without requiring a level of community interaction.
It may be better to have a 'minim effort' level? Like, fill out sidebar, have one post every X months, something like that?