I think the fediverse does have a privacy problem, however as long as your account can’t be linked to you (malicious instance, your email being breached) it doesn’t matter all that much (at least for my threat level) because the info is confined to the fediverse, where little can be done with it, especially if you swap instances/accounts commonly. Yes, one could create a profile on you based on what you upvote/downvote, but they can’t for example use that to serve targeted ads, because the fediverse doesn’t have a ad network and when visiting other sites they can’t associate your profile with you (assuming you don’t reuse your username), unless I am forgetting something.
tldr: The fediverse isn’t private, but the data is practically useless
I think the fediverse does have a privacy problem, however as long as your account can’t be linked to you (malicious instance, your email being breached) it doesn’t matter all that much (at least for my threat level) because the info is confined to the fediverse, where little can be done with it, especially if you swap instances/accounts commonly. Yes, one could create a profile on you based on what you upvote/downvote, but they can’t for example use that to serve targeted ads, because the fediverse doesn’t have a ad network and when visiting other sites they can’t associate your profile with you (assuming you don’t reuse your username), unless I am forgetting something.
tldr: The fediverse isn’t private, but the data is practically useless
Most people, however, are not that careful about partitioning their accounts (myself included, frankly).