When viewing the history of tag wikis, I've come across quite a few tags showing that the original revision was by the Community user, and quite a few that were by normal users. Two random examples I've come across are languages and profile-picture. When viewing the tag wiki histories, you can see that profile-picture was originally created by Community, and languages was originally created by a normal user.
I've also found that, when going to
Activity -> All Actions -> Posts in a user's profile, there's a certain type of post called
wiki, which seems to be the creation of a tag wiki. You can see this in the Community user's profile.
I never see an option to create a tag wiki when I'm creating a tag, though that might be because I don't have tag wiki edit privileges.
When are tag wikis shown as being created by normal users vs the community user?