Hidden activity log
No idea if this has already been pitched or not, but as a firm we have a community notice board where people can come and leave notes for things, positive messages etc.
We wanted to add a level of anonymity to it, by hiding the activity log from everyone except facilitators, so we can moderate what is posted, but not let the rest see who dropped them a message or posted about them. The private mode is great, but it doesn't stop you from seeing who posted what in the activity log.
I feel like this wouldn't only help myself, as this could be put to use in many other ways, such as boards where people can go drop their worries/thoughts & feelings, can go drop ideas for staff/community events, or even where people can post something positive about their staff in secret to help boost moral.