Over the years I've written and spoken about Section 230 of the Communications Decency Act. Here's my lexicon entry that covers the subject.
It's pretty simple. It's a public forum and protected under Section 230 as long as there is minimal editing or moderation.
If the platform changes content, puts on special labels, or changes the algorithm to suppress search functions, that's when the platform becomes a publisher and is no longer under the protections of Section 230.
The law is clear. Some big tech companies want the protections of Section 230 while acting as publishers. This should not be allowed. Our problems now are because the law as written is not being enforced.