I assume you accidentally created another account, and you are the author of the linked question, which was posted from an unregistered account. Had you been signed into the account you posted the question through, the system would have notified you that your question received a duplicate vote:
This question may already have an answer here:
[Title of question]
That solved my problem! No, my question is different. I will edit to explain how.
To respond to some of your statements:
I can't post comments because I don't have enough of reputation.
While you do have to wait till you gain a reputation of 50 to comment everywhere, you can comment on your own post regardless of reputation. As you have logged in from another account, you can't comment on that question since it's not from the same account.
And why is the community so unsparing (down votes for a legit doubt !)
From on topic page:
Please look around to see if your question has been asked before. It’s also OK to ask and answer your own question.
Sometimes users downvote a post because they think the OP has not shown some research effort before posting a question. The original of your marked duplicate is a high voted and popular question too (~67k views). The users might have downvoted because they think you haven't searched properly before posting the question.
What am I supposed to do?
Since you have asked a question from an unregistered account, you were not able to see the duplicate votes or to comment on your post. Request that both the accounts (unregistered and registered one) be merged. For help in merging accounts, see I accidentally created two accounts; how do I merge them?