This is primarily a PSA to get users to be sure that tag wiki content is not plagiarized.
The fact that only 20k+ users can edit tag wikis without being reviewed first carries quite a bit of weight here, as there are only 41 users with this privilege on all of Arqade. (Even less, considering that 8 are moderators and 1 is a Stack employee who have the privilege regardless of their rep, as noted by @Robotnik in the comments)
On top of that, only 241 users are eligible to review suggested edits to tag wikis and their excerpts, as that privilege comes with having 5k+ rep. However, I've rejected two blatantly-copied suggested tag wikis, only to see them get approved by two other users. This pretty much defeats the purpose of assigning these privileges to such high rep numbers.
From the Tag Wiki review rejection reasons:
This edit copies a significant amount of content from an external source. Generic descriptions such as encyclopedia articles and ad copy do not provide useful guidance; try creating something useful to this community specifically, and be sure to attribute the original author. See: How to reference material written by others.
Simply copy-pasting the bodies of the following tag wikis into Google brought me to external pages with the same text as the tag wiki.
Example 1: Paladins
Paladins: Champions of the Realm is a hero-based cooperative shooter with strategy and deep character customization. Through a unique collectible card system, players can amplify and augment a character’s core set of abilities to play exactly how they want to play.
Simply googling the body of the tag wiki brought me to the Steam store page for Paladins, which features this description:
Enter a fantasy world of ancient technology in Paladins, a team-based shooter with strategy elements and deep character customization. Through a unique collectible card system, players can amplify and augment a character’s core set of abilities to play exactly how they want to play.
I have bolded the parts that are identical between the two.
Example 2: Super Mario 64
This one is a bit older, but seeing the previous tag wiki be approved brought the super-mario-64 tag wiki review to mind.
Super Mario 64 was the first 3D Mario game first released in Japan on 23 June 1996. It is considered a 3D platformer where the player controls Mario through several courses. Each course is an enclosed world in which the player is free to wander in all directions and discover the environment without time limits.
It was the best selling Nintendo 64 title, with over 11 million copies sold. The game had ground breaking 3D technology, and is critically acclaimed to be one of the best and revolutionary games of all time.
While less blatantly plagiarizing, copy-pasting the first paragraph into Google brought me straight to the Super Mario 64 Wikipedia page, where you can find the following passage under Gameplay:
Super Mario 64 is a 3D platformer where the player controls Mario through several courses. Each course is an enclosed world in which the player is free to wander in all directions and discover the environment without time limits.
I have again bolded the identical parts between the tag wiki and Wikipedia article.
That said, there have only been maybe three or four suggested tag wiki edits total that I have reviewed so far that have been blatantly plagiarizing, but the fact that two of them have gotten approved is a bit upsetting. Plagiarized tag wikis aren't extremely prevalent, so this isn't a huge deal, but I believe that Arqade (as well as all SE Network sites) is against plagiarism. Thus, I think it is important for reviewers, especially tag wiki reviewers, to double check before approving.