Doesn't the main issue lie in platform specific features? For example, after syndication on Twitter someone DMs you with relevant information to your post.
It's imo the problem with something like GitHub as well. Git is already decentralized and if you push to GitHub you still have your local copy of the repo. But then if someone creates a pull request on the platform not only do you have to use the platform but some data will stay on and only exist on the platform.
But you don’t have to monitor or respond to DMs. Your profile can contain a suggestion to use email. On Github, the README or whatever for your project can ask developers to please email patches, or fork, but that you don’t pay attention to Github pull requests.
It's imo the problem with something like GitHub as well. Git is already decentralized and if you push to GitHub you still have your local copy of the repo. But then if someone creates a pull request on the platform not only do you have to use the platform but some data will stay on and only exist on the platform.