That is as may be (though I'm not sure it's quite as dire as all that), but I'd argue that if it isn't true that anyone can edit and see their changes instantly then it isn't really a wiki.
That doesn't mean wikis can't have bans, require captchas, or lock pages that are frequently abused to tenured registered users, but the tooling needs to support instant updates and freedom to edit needs to be the default. Otherwise you're looking at a static site or a CMS, not a wiki.
Yes, I agree with your point that a realtime edit/publish cycle is a key part of the “wiki” aspect, instead of needing to do a build. I hadn’t considered that part of it.
The most popular wiki sites just means that the community has to police the problem. Someone has to police the problem or else, even without spammers, you have people fighting grammar and typography wars over the math subreddits. You wake up one day and realize someone added their favorite kind of commas to every sentence across every major math article.
