Check out this example where @blizzz is on a different instance:

The handles he mentions should be correctly highlighted and linked to their respective accounts. It should also always be the short handle and not show the other person鈥檚 server in the message.
FYI: the quotes are better managed in 0.1.1: https://github.com/nextcloud/social/pull/255
Bugfix proposed at the linkify upstream repo: https://github.com/SoapBox/linkifyjs/pull/257