This is a problem that every “we made a comments layer for the entire web!” project has faced.
There is an option for publishers / site owners to natively add Kontxt directly to their site with a single line of javascript to give them an initial point of control and moderation (view only, comment, or user added highlights). However, sites can have multiple highlight layers with different privacy controls, so users can switch to another layer for discussion for something like research.
Privacy controlled layers are only accessible to those they're shared with and there's only one public layer per site. Laws will always be followed. And cruel behavior on the web will likely be addressed as it is elsewhere today. It's too early to have developed any firm policies around, but it's definitely important and will be watched and addressed as needed.
We can self police for politeness, and keeping people on topic but the moment people start using a venue to organize harassment, the victim and venue owner ought to be able to rely on a higher party to adjudicate justice.