Pirat In the extension it is not implemented
Most of the extensions here started out as a proof of concept. A developer trying a shot at extension development and then trying to keep up with demand (or the lack of and fading away into real life reponsibilities). You cannot expect extensions to suit all needs of every forum and each webmaster. If you need it that badly I suggest you pay the maintainer of the extension for the feature or hire a developer to add the functionality you need. In the end you're using their code for free anyhow.
Pirat I am sure that this can be improved in 2 lines
Please do PR that functionality to the repository, so that the author can include it in the next release. The GitHub repository: https://github.com/wiwatsrt/flarum-ext-best-answer GitHub has an online editor which allows you to PR right after editing, so that makes contributing even easier!