YouTube is in fact a great example of this being a real problem - they infamously chose to reduce the visibility of non-mainstream news channels, drastically cutting their viewership while not removing a single video from their platform. They also often de-monetize videos for even mentioning certain words or subjects, greatly dis-incentivizing anyone from discussing them (e.g. rape can't be discussed on YouTube if you want to make any money from your video).
...and just like in a government censorship context, ambiguity and fear do a lot of the work. Rules are not clearly defined or consistently enforced. You don't necessarily even know that you are being disciplined. It's best to just stay far away from controversial material entirely.
On youtube, it's had the curious side-effect of specialization.
It's not worth occasionally discussing political content, social issues or controversial content. A youtuber risks harming their income/success by taking a wrong step. Meanwhile, you kind of need to be specialized in order to know where the lines are.
For example, the Ukraine/war content youtube allows, bans or demonetizes currently is not the same as it was 3 or 8 months ago. The rules aren't written, and you need to be immersed and current to even guess what they are.
Same for sexual violence, Trump or any other highly contested moderation issue. You really need to be a specialist to (a) stay within moderation lines and (b) be worth the risk.
YouTube is in fact a great example of this being a real problem - they infamously chose to reduce the visibility of non-mainstream news channels, drastically cutting their viewership while not removing a single video from their platform. They also often de-monetize videos for even mentioning certain words or subjects, greatly dis-incentivizing anyone from discussing them (e.g. rape can't be discussed on YouTube if you want to make any money from your video).