In twitter.activitypub.actor, all the data (images, username, bio) are scapped from the server side because I wanted to respect the users' right to privacy, even if it cost much more on my side.
In my opinion, if Mastodon coders want to implement mention as link, they might use a confirm dialog box when clicked and show a difference between mention of actor and mention as link in the statuses.
Generalistic and moderated instance. All opinions are welcome, but hate speeches are prohibited. Users who don't respect rules will be silenced or suspended, depending on the violation severity.