To receive webmentions you have to install the IndieConnector plugin and configure it. IndieConnector will handle all the webmentions and normalize their data. Currently only webmention.io is supported. After installing IndieConnector, Komment will automatically be informed about new webmentions.
Webmention support is enabled by default but won't work until you install IndieConnector.
The first version of the Komments plugin allowed sending webmentions and mastodon toots when publishing a page. This is deprecated by now!. Please use the IndieConnector plugin for that!