Part 1. On Stack Exchange voting
I've downvoted this primarily because of the assertion that "I know the voting system here doesn't work." I disagree.
The voting system isn't foolproof – what voting system is? However, in general, Stack Exchange voting seems to work fairly well. Most of the time, there is a pretty good correlation between the overall quality of an answer and the number of upvotes or downvotes it receives.
It's worth remembering: it's hard to judge the quality of an answer because there are so many factors at play. One answer may offer great insight, yet contain a minor inaccuracy somewhere; another answer might be completely correct, yet it doesn't provide much substantating evidence or explaination; still another answer might give good information, but be formatted sloppily with spelling and punctuation errors. Such partly-good/partly-bad answers are probably justifiably upvotable or downvotable, for the various reasons given.
Part 2. On the plural of belief
As for the answer that prompted this thread, I think you make one very problematic statement:
The reason to use beliefs is to prevent any confusion.
Hmm. I don't think any editorial boards or dictionary editors got in a room one day, and said, "Let's pluralize beliefs with an f and s to prevent any confusion." That's a very misleading and oversimplified statement. Worse still, it contradicts an example you give later in your answer: halves. If we pluralized beliefs to "prevent any confusion", then it would stand to reason that we would write halfs to prevent any confusion as well. I find that unexplained contradiction to be very sloppy work, and potentially confusing for the learner. I see no problem with these downvotes.
More telling still, when people tried to reason with you about this, you only became more stubborn:
I don't see any valid point in your comment.
That comment has double-digit upvotes, yet you still responded confrontationally. Your attitude reminds me of the joke where the young boy tells his parents, "The whole marching band was out of step except for me!"
Part 3. On the negative remarks found in this post
I believe you would understand why the voting system here doesn't work and why I don't care about it.
I doubt that's true. If you really "didn't care" about the voting system, you wouldn't raise a stink in such a negative way, and you wouldn't lodge so many petty disputes in the comments, like this one:
considering there are hundreds (maybe thousands) of lousy and even horrible answers saved in this community
That's a bit negative. If you think an answer is giving bad guidance, either downvote it, leave a comment, or do both. (Comments would be the more constructive option, because you could explain why you think the answer has problems.)
Overall, I think you'd be best off following Colleen's advice. When you get downvoted, keep an open mind rather than an argumentative spirit, and look for ways to improve your answers based on the feedback given.
So any answer trying to show some patterns (with real examples) will be punished while any simple answer that can be posed by any primary school student get upvoted. Do you think it is fair? I don't.
This is very telling. This isn't a matter of "punishment" or "fairness", this is a matter of you wording an answer in a very misleading way, and refusing to listen to anyone who is trying to point out legitimate problems with your original answer.