Firefox has long supported mailto://email@example.com as a way to handle sending an email to the designated person. To make federation of social media more mainstream, democratized, and user friendly, Firefox should support an activitypub://firstname.lastname@example.org URL protocol.
Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.
`email@example.com` is not an ActivityPub id and has no meaning to ActivityPub. An ActivityPub id is actually just a URI. At-handles are a convenience Mastodon borrowed from Twitter for referencing users and they require a separate protocol, WebFinger, which not all AP implementations will support.