This comment made me think a bit about the natures of freedom of speech and spam (where "spam" partially includes the scenario that you're referring to). I've

This comment made me think a bit about the natures of freedom of speech and spam (where "spam" partially includes the scenario that you're referring to). I've come to the conclusion that they're two completely separate problems. You can have spam with no freedom of speech, freedom of speech with no spam, or anything in-between, depending on implementation. The problem with conventional spam is that e-mail accounts aren't usually tied to real identities (although that's arguably a good thing), and phone numbers aren't authenticated at all, and you don't need any sort of permission to call someone or send someone an email. This isn't the case with social media platforms (and their analogous "spam"), either existing ones or theoretical ones. Signups are throttled and somewhat tied to a real identity - although even if they weren't, you can easily design a system where, say, you can't send someone a message without their permission (which some platforms e.g. Instagram do), or accounts are un-discoverable by default unless you make them visible. Additionally, virtually every social media platform in existence gives you the ability to block users (and, very few, if any, people claim that "free speech" means that arbitrary users on a platform can't block you - almost everyone focuses on bans from the platform itself - and you're conflating the two). Therefore, the virtual equivalent of "five people shouting in my and your ears" is not an issue because there's no virtual equivalent to "blocking" someone IRL, which trivially fixes this problem. You're conflating "forcing everyone to hear me" (which very few people think is a good idea) with "having a presence on a platform" (which is the issue actually under contention). In short, the issue that you're describing can be pretty trivially dealt with even when a platform has "perfect free speech" and does not remove any content that it is not legally required to. ...and, because the issue is a non-issue, it doesn't reduce freedom.