It would be a nightmare to implement a wiki over activepub, so it would probably need to exist outside of federation.
It also feels like the kind of feature creep that made Reddit unsustainable. Software should do one thing and do it well - Reddit's reliance on 3rd parties fixing core functionality while they pursued every shiny new thing their product managers and software engineers wanted to put on their CV should be a cautionary tale.
I feel we would be better served with wikis stored outside of Lemmy and simply linked in the description. Lemmy exists on the web and shouldn't try to pretend it doesn't like corporate social media.