Sorry for my ignorance but why would it be a nightmare to implement over Activitypub? Would there be an issue with approved editor accounts from other instances?
I don't know if I would consider wiki pages the threshold for feature creep. It's been a basic feature for Reddit mods ever since I joined Reddit 10 years ago. Therefore it existed before all the new.Reddit features were thrown in. Mods use wikis for directories, tutorials, archiving select content, and bot configs. Yes you could link to external wiki pages but IMO the experience for reading, editing, and adjusting settings would not be as seemless.
Sorry but I fail to see why support for wikis would be synonymous with corporate social media. IMHO, it's a fundamental tool to have.