I can understand where you're coming from, in that you authored the data. However, that's different from ownership. That's determined by the terms of service of

I can understand where you're coming from, in that you authored the data. However, that's different from ownership. That's determined by the terms of service of the website. If you want to retain full ownership of the content, in some (many?) cases you can only do so by not commenting on their site (or service used by the site), but rather commenting on a site you control. While some people may have an expectation that the site has a responsibility to steward the content provided by users, and I think that's a laudable goal, at the end of the day that is determined by the terms of service.