To be honest, this is quite an old plugin so there’s a chance it could be converted to a theme component now. I know some of the others have made that leap. I’m afraid I don’t know specifically if it would be possible with this one though.
Does this also create a tooltip for topics referenced in text of posts? Also, would using the API of Discourse and loading the topic content on demand (thereby not requiring it to be a plugin, merely a JS-based enhancement) be a solution?