The modmail has been copied below. The announcement is linked in the first comment, and people are justifiably annoyed.

Hi Mods,

We are in the process of rolling out a big overhaul to Subreddit Wikis, including a new layout, tools, discoverability, and more.

TL;DR - We’ve given wikis a makeover. The improved wiki (launching next week) includes: new tools and layout, additional safety features, more edit access options, and improved discoverability. For those with wikis built on old.reddit, we’ll move your existing content over, so that everything is preserved. Edits made via old.reddit after the migration won’t sync to the new system and vice versa.

Keeping a wiki fresh and up to date can be time-consuming, and mods shouldn’t have to do it all alone. As part of this update, “successful contributor access” will be enabled by default for your community wiki the week of July 14.

• Successful contributors are based on their past posts/comments within your community and high contributor quality score

The entire wiki or individual pages can be restricted to “mod-only” editing at any time (after the above changes are made) within “Wiki settings” found in Mod Tools on desktop.

This setting manages for quality and safety while enabling more Wiki maintenance support and relevant content creation. In early testing, subreddits with this setting enabled did not require mod revisions.

To opt out of this setting being turned on in your community before July 14, please let us know via this form.