Earlier quoted context omitted.
> They're private platforms. You can send those links via many other routes ... That is a complete non sequitur. You say it's not about freedom of speech. Someone responds that, in fact, blatant censorship is occurring. You don't even attempt to refute this point, instead falling back to pointing out that the censorship isn't illegal! Censorship reduces freedom to speak. That statement remains true whether or not the…
Removing spam could be considered a form of censorship. It is removing the speech of others. Generally anti-spam measures facilitate rather than inhibit freedom of speech. A sufficiently popular internet forum without spam controls would quickly become mostly unusable. In this case, doesn't censorship enable freedom to speak?
The problem with such an analogy is that spam is inherently off topic - approximately none of the other participants actually want to see it. That's fundamentally different from this case. Whether you deem it misinformation or political speech, many of the participants clearly do want to see it. In fact, they want to see it so much that such information is consistently selected by the automated algorithms that are designed specifically to maximize engagement metrics.