In this website as far as I know we are allowed to down vote any answer or question by losing 1 rep. The problem with this system is that people with bad ethics can answer a question and down vote the other answers despite them being good or not. What I want to ask here is why is it even allowed to down vote answers in a question answered by you? It should be only allowed to vote in other answers, if you do not have any answer in that same post.
1 Answer
Similar situations and issues to the one you describe sometimes happen. It occurred to me that I downvoted a post and I left a comment. Moments later some of my posts were randomly downvoted (see e.g. Taking revenge on me because I publicly downvoted and commented). Nonetheless, I believe that downvotes (and upvotes) should have a mandatory associated comment that motivates the downvote, in a similar fashion to the peer-review process that research papers need to go through. This feature or similar ones have been requested by several members of the SE community. See e.g. these discussions https://meta.superuser.com/q/7223 or Encouraging people to explain downvotes.