Wikis benefit more from the ability to mirror them and to link between them than they benefit from full federation. You need much better antispam on a popular wiki than in most other user content systems, and that's not solvable with just blocklists like in many other federated systems. You need almost all antispam working server side, the user side fixes doesn't work effectively.

It would be useful with atproto (bluesky) style portable identity where you could log into other wiki hosts from your own hosts user account to submit stuff (allowing you to maintain a single account in federation through OAuth logins, while still allowing each wiki to be centrally managed) with support for mirroring and native cross-linking between mutually trusting wiki hosts. You could replicate the Wikia/Stack Exchange user experience this way, without all the ads and without any central gatekeepers. (Very similar to stack exchange actually, as each individual Wiki would be read-only to you until you login to it separately (still using one a single account))

Things like content addressing could allow proper static links that survive page name changes for the cross-linking, etc.