because every other instance does the same.
this comment is content, it’s now stored on the instance I share it with, and all the instances it federates to, along with my username and so forth.
the above is just a legalese explanation of how the fediverse works.
Maybe it‘s a legalese explanation of a problematic aspect of the fediverse though. When a commercial entity comes in that deals in people‘s data, which doesn‘t just store data on its servers, but creates a product out of the data. And it seems like it can do that here without you ever agreeing or even knowing about it.