There doesn't seem to be an obvious way to remove content (like issues, merge requests or comments) easily from a project or ban contributors from participating, ie, ripe for abuse by 4chan or whoever wants to set the internet on fire today.
There was a project, mango [0], that was very similar to this. In addition to using IPFS for storage, it used ethereum for things like permissions control. Unfortunately it hasn't been updated in a while, but perhaps this will bring some attention to it?