I just had someone literally call me a dimwit and lazy and then suggest that I was on the spectrum. I did not retaliate in kind but simply asked about his education. He said he had a PhD so I asked him what his PhD was in. He refused to answer and continued to call me ignorant. I bet you he blocked me. I was never rude to him but he didn't like not getting everything his way.
It depends on the type of communication. E.g. if you are in a private conversation, you can leave it and won't get further messages in that conversation. (Without using the Ignore function.) Then, the username won't be shown in the participants list anymore. Though I don't see a reason why you would want to know whether someone ignores you one way or another.
There is a difference between being blocked and being ignored. I'm not sure if you have blocking on here or not. At the time, I was more concerned since he was being so vicious that he might take his vitriol to the forums or attack me in other places but that hasn't happened so I'm okay.
It shouldn't be possible to figure out if someone blocked you. That information can be used by harrassers (which I'm not saying you are!) to move on to a new account and continue their harrassment. Big no.