I just blocked a woman 1 hour ago, she blocked me and we had not had any form of argument or anything. I just went to reply to a mention from a person on her question and I couldn't. While I do not really care I do think it is really odd that people block you when nothing bad has happened or you have not talked to them much.
Just fine. I get it when you want to block someone for reasons of harassment or utter disrespectful discourse, but I remember getting blocked more than once simply because I respectfully disagreed with someone's opinion, which is just petty and lame, but what can you do? It's the Internet after all.