The question Free wiki-like webapp with internationalization, no ads, anyone can edit, mobile-friendly was closed by a mod, referencing the meta-discussion Are hosting recommendation requests on-topic?.
In my opinion,
- that meta-discussion does not apply to the question, and
- the question is on-topic and should be reopened.
Are hosting recommendation requests on-topic? does not define what "hosting" exactly means, and the discussed question is deleted, but skimming the answers, it seems that it’s about web hosting services.
I don’t want to give a full definition here, but I think it’s safe to assume that not every hosted service which can produce web pages (GitHub, Tumblr, Google Docs, Dropbox, Flickr, …) is necessarily also a web hosting provider.
If the OP had a specific wiki in mind and was looking for a service to host an instance of (or even install) this wiki, I’d agree: off-topic as asking for hosting.
But the OP is looking for software with specific requirements (a wiki) hosted/managed/offered by a web service. Are web service recommendations off-topic? applies here.
The tag web-apps says (emphasis mine):
The web-apps tag is used when requesting software that has an interface appearing in a web browser. These applications may run on third party servers or be self hosted.