Are multiple youtube accounts subject to suspension/termination if no proxies are used and if I use them to only comment/video-respond and like comments?

If you have 1-4 accounts form the same computer, you won't get banned. (I don't know how suspicious it'll be)

But the bad thing is, that once you get 1 account banned, they will check the other accounts that were registered through the same IP.

Hmm, alright but what's the worst that can happen? Are they likely to all get banned? I read somewhere that it's allowed to have multiple accounts but some other people are skeptics and I don't want to lose time and efforts checking out myself.

It's allowed to have multiple accounts as long as you don't violate their rules.