In general, the privilege to select the best answer should rest with the author of the question. This is an ultimate tool for them to say "this answer helped my particular case the best". If the author decided not to select the best answer, we should respect that and not select the best answer ourselves (even if the user is no longer active).
As a community, we should intervene only when the selected "Best answer" is hurting the quality and reliability of TibiaQA. If it becomes obvious that the current "Best answer" is no longer correct because e.g. another answer links to the official source of information and it proves the "best answer" is wrong, we should start a discussion on Meta TibiaQA with a request to change the best answer. The community and moderators can then decide to change the best answer, or at least remove the "best answer" sign from the existing answer.
Another thing that we might consider changing in general, is not having the "best answer" displayed as first by default. In which case only the amount of votes would determine the position of the answer. The community could then easily downvote the incorrect answer so that the correct answer rises to the top. Thoughts?