There are several types of "shadow banning" on social media. This page will give examples of comments which appear to be hidden by Youtube moderators, as opposed to comments deleted by a channel 'creator'.
Twitter was famous for hiding comments by "low status" users, and using other means to discourage certain views.
One commonality among social media in he U.S. is that individuals whose comments are hidden are not made aware of it.
Here is a comment on the Youtube video https://www.youtube.com/watch?v=f4pD8TkO9k4 that is only visible to me, and only when I am logged in to that Youtube account.
There is an interesting use of these kinds of experiments which most psychology students are not aware of. Years ago 'brainwashing' was studied for military uses, by scientists who generally had an analytical background, which was the main school pf psychology until about the 1960s. Today Analytical Psychology has largely been replaced with pharmaceutical and 'melting pot' psychology.
It was found that the only reliable way to 'brainwash' was to prevent an animal or a person from having a space to which it could retreat and recover, a space Jung called 'Temenos'.
So these animal experiments that look at reactions in stressed animals while preventing those same animals from having space to recover from that stress, can also be used to learn how to brainwash humans.
Most psychology students ignore these experiments but some can turn them into lucrative professions. Jim Mitchell and Bruce Jessen made a fortune doing that. I had a professor that trained one of them, Dr Madigan, a very great guy. In fact I took a behavioral psych class with him years ago and I remember he used to be cautious about conversations involving the fact that each mouse we were working with was euthanized rather than, for example, given to the zoo to feed eagles etc.
Youtube has at least three different 'visibility levels' of comments.
Sometimes a comment is completely removed i.e., not visible whether logged in or not. These appear to be comments deleted by the owner of the channel.
Sometimes a comment is visible only to the original poster, and only when logged in, as the example above.
Sometimes a comment will be served to a viewer from a different server than other comments, and it isn't clear what the significance of those comments visibility might be.