People WILL lose interest and not re-engage - that's the default state for any social network. You have to figure out why they would come back - is it to re-con

People WILL lose interest and not re-engage - that's the default state for any social network. You have to figure out why they would come back - is it to re-connect with someone they spoke to, or to read some new content on the site, or to express again how they are feeling? And how do you make this all easy through the features you build? You can start with some basic Code of Conduct that let's say Github, Reddit or Twitter uses - no need to reinvent the wheel. Then you can modify it as time goes to suit what's working or not for your community. If you have a good model for iterative improvement that puts the user in the loop somehow, it'll be reflected in your engagement stats.