I don't know which add-on they are using, but Frontier Developments manages to do that just fine on their forums.IIRC, the last time it was talked about the most feasible method to implement (i.e. not something that would have to be developed in-house) would have to check every post in every thread listed on the page being viewed for posts by users on a list of devs and update the formatting for those threads individually each time a page was called. To say it would hinder performance is an understatement. This post from a XenForo dev is dated from 2013, but it meshes with what I've heard and read more recently about the potential for such a feature. In summary, it would be very easy to highlight threads which are started by a dev, or where the dev was the most recent post, but information about all the posts between isn't available at the same level and so would require a much more intensive search process.
It's also a direct link to the first dev post and you can jump to the next dev post by clicking the icon below their name.