Or Youtube did it automatically. They do it all the time. Ian, by his own admission, doesn't have much time every day to read comments.
In my experience, there are three layers of a comment shadowban on YouTube. All of them can be verified by opening the video you've commented on in incognito mode. If after 1-2 minutes from posting it you can't see it in incognito mode, it's been shadowbanned, It's also how you can verify which type of a shadowban it is.
First one is the algorithm, which is schizophrenic and acts randomly on single comments. That's why you'll often see comment chains on inactive channels with seemingly missing replies. It never acts on an entire channel, it's global, it's always active and creators can't disable it.
Second one is channel word filters. Those will act the same way the algorithm does, but, again, on word filters. If you can post an innocuous comment and it goes through, but another one with a word that would show up on another channel doesn't, that's a word filter shadowban.
Third one is a channel-wide shadowban. This one can only be done by creators and channel managers. I know that I've been shadowbanned from Louis Rossmann's channel after engaging in a livestream chat once. Louis would otherwise respond to comments that I'd believe to be too much so I know he wouldn't be the one to do it, but his chat jannies would be more likely to, so it seems that a livestream chat ban and a comment ban is one and the same.
Not a single one of my comments will show up on any of Ian's videos. I could post it on another channel where I know I haven't been shadowbanned by the creator and it would show up. But not on Ian's channel, or on Louis' channel, where my account has been shadowbanned from. This excludes the algorithmic shadowban, as well as the word filter shadowban, as those wouldn't apply 100% of the time. A channel shadowban does, and that's what I'm experiencing on Ian's channel. This means that if Ian doesn't have anyone managing or moderating his channel, he was the one to shadowban me, and I remember that at that time I was posting some mildly controversial comments that I double checked wasn't algorithmically hidden, like I do with every YouTube comment that I post to make sure others can read it.
That personal experience of mine, as well Ian's other actions that were described in this thread lead me to believe Ian is exactly the type of politisperging spastic to burn his career into the ground if he doesn't keep his retardation in check.