No one can add categories to mainspace articles right now, because the vast majority of pages should be properly categorized at this point and 99% of the times people add categories that a) don't exist and haven't been discussed or b) are out-of-universe and would never be approved, and c) 100% of the times of the former or the latter, they flood the recent edits page.
Hello Thailog, in case you haven't read the Community Central blog from earlier this week, Fandom officially announced the Editor Rewards program. Fandom has been looking for ways to give back to users for the work they've done. Recently they have done things such as buy movie tickets, or offer products from their favorite fandoms. Stay tuned as perhaps you, your co-admins, or other contributors for this wiki may even be eligible!
If you have any questions, feel free to comment on the blog so the Editor Experience team can answer directly.
But it's a good, neutral description. "Anti-Light" is a fan originated term, and if we use that as a page name, people are going to think it's canon. Not everything needs a page; there's plenty other work that needs doing.
If I recalled Tim Drake aka Robin did call their secret society the "Anti-Light" and since then it became canon and fans have been referring to their team as such. I really don't see the harm in creating a page focusing on that team.