@rogerscrafford @Johnphilpin @manton I think it’s an exaggeration to say

You effectively make them co-owners of your content.

You give them a licence to do pretty much anything they might want to do, and this licence lasts forever and can’t be revoked. But, subject to the licence, you remain the owner. You can crosspost, repost, move to another platform or site, delete, and almost anything else you can think of.

They can even sell it.

Theoretically perhaps. But given the rights that you retain in what you have written it’s not at all clear that what they have to sell has any economic value.