Please bear with me as I don't know exactly what I'm suggesting yet, but I need help fleshing out this idea.
If I search "wordpress and discourse on same server", I get this result:
4 closed topics. All technically good matches as far as the search algorithm is concerned, and they will take me to the How-to I need in the end because they all link to it. However, 4 closed and near-identical topics are hardly ideal as top results.
What you really want is to send the searching user directly to the topic they all linked to before getting closed, the solution to each of these support posts, which is "Running other websites on the same machine as Discourse".
Therefore I'm suggesting:
If the last post in a closed topic contains a single link to a different forum post, or;
If the Solution (using Solved plugin) contains a single link to a different forum post, then:
The linked-to post (usually a topic) will take on the incoming link's topic title as one of many aliases. Locked topics will be down-prioritised slightly, so that the topic with the alias rises above them in search results.
So could this work or does it sound like I'm off my meds again?