> How does a host say how to find them on Mastodon (or ANY ActivityPub based platform)? They might say john@reallycoolpodcast.co.uk

Tell a non-techie "@johnsreallycoolpodcast" and there's a good chance they'll figure out it's a Twitter or Instagram username.

Tell a non-techie "john@reallycoolpodcast.co.uk" and they'll think it's an email address or at best infer the website URL from that.

Tell a non-techie there's a social media platform called "Mastodon" and they'll look at you funny, and after the initial awkwardness they'll dismiss it because they don't understand (nor care!) about the whole decentralisation aspect of it and how to navigate its inherent downsides.

Having Mastodon use email-like identifiers is a cute technical detail but is not only completely irrelevant for non-techies but actually hurts adoption as it's less recognisable than an "@username".