I flagged number 4 for moderators' attention, and the posts were undownvoted with the flag considered helpful, so I'm guessing a moderator undownvoted them, or maybe they were undownvoted by the system. Since then, the other three posts were downvoted. All downvotes were without a comment.
I don't consider any of these posts a great one, and I can understand downvoting some of them. 3 is a poorer version of Brian M. Scott's argument, which I even deleted at some point to undelete it later after talking about it to Brian in chat. Number 5 can be considered irrelevant to the question, although I think it's relevant enough. Anyway, I don't mind the posts being downvoted, but the fashion in which it is done is a bit irritating.
I would like to ask the downvoter(s), if they're reading this, to comment on the downvotes so I can learn from my mistakes. Also, if the downvoter(s) don't reply, I would like to know if anything can be done about it. What worries me the most is that I may learn to ignore the downvotes, believing they're all dishonest. The only (I think) time I was downvoted before, I took it seriously and looked at my post closely to see what could be wrong with it. I don't remember if I found anything serious because it was some time ago, but I think the downvoter did the right thing if they thought the post wasn't good, and they had a reason not to leave a comment. It is useful to me to know that someone didn't like my post. But when I start suspecting that someone dislikes me personally or is just bored, the downvotes stop being useful, at least to me.