Two days ago, I deployed the official wiki for lemmy.dbzer0.com. It's using django-wiki as a software, which other than being markdown-based and therefore helping lemmings easily migrate documentation over, provides python hooks for doing some really cool stuff.
For example my current version is tied to my lemmy instance. This means that while everyone can read the wiki, only registered users of my instance can edit articles. This helps prevents the usual problem of open wikis, which is drive-by spam articles, and ensures that only people with interest in the wiki can use it.
I plan to extend this integration in the future. I am thinking things like minimum account age to edit all or some pages, profile pages which enable even tighter integrations, being able to specify "trusted instances" which would allow edits from their users as well, and so on.
But that's not all, the same approach I used, can also be used to integrate with any fediverse software, like mastodon. This means each instance could theoretically have its own wiki to extend the information adjacent to it.
I'll soon (I hope) will provide an ansible playbook that anyone can use to deploy it which will also provide my custom code to integrate with lemmy.
Reddit had the ability to have a per-subreddit wiki. I never dug into it on the moderator side, but it was useful for some things like setting up pages with subreddit rules and the like. I think that moderators had some level of control over it, at least to allow non-moderator edits or not, maybe on a per-page basis.
That could be a useful option for communities; I think that in general, there is more utility for per-community than per-instance wiki spaces, though I know that you admin a server with one major community which you also moderate, so in your case, there may not be much difference.
I don't know how amenable django-wiki is to partitioning things up like that, though.
EDIT: https://www.reddit.com/wiki/wiki/ has a brief summary.
Indeed that is also what I had in mind regarding linking up a Wiki to Lemmy.
It should be possible I guess to link community membership to wiki groups and those groups each have their own name-space that looks like a seperate wiki more or less.