Is this allowed and encouraged especially when one is commenting on the others posts.
Multiple accounts are usually tolerated, but they are not allowed to interact at all. If you are e.g. just using a different account to ask a question anonymously, this is allowed as long as you don't vote on it, don't circumvent any rate limit on it and don't interact with that account in any other way.
Interacting with your own accounts, and trying to give the impression that they belong to different users is not allowed.