YouTube sucks in every way. They delete comments without telling you, suspend and delete videos and channels randomly and incompetently, demonetize based on bizarre and arbitrarily applied policies, steal creators' revenue on lame pretexts, and offer no redress or customer service to speak of, just boilerplate emails which make it clear you're being ignored, or, of late, a dumb AI which tells you you're wrong. But because they have a virtual monopoly they can get away with all this.
The only recourse that ever seems to work is hitting their support accounts on Twitter, such as TeamYoutube.
Search on Google for "YouTube deleting my comments" or the like, and you'll find hundreds of people complaining about this. I've had harmless normie comments deleted with no explanation. They're just gone two minutes later, and you won't even know unless you check back.