How to reproduce:
- Go to Beta on preferences and make sure "New filters for edit review" is enabled
- Add user JS with custom mw.hook( 'wikipage.content' ) and inject some content to each entry (such as new button/link/whatever)
- Open RC page - the content will be injected twice
- mw.hook( 'wikipage.content' ) is fired once (regular page load)
- mw.hook( 'wikipage.content' ) is fired on model change on the filters - this is fine when the user is changing the filters, but less cool if the model was just initialized
This should be fixed to avoid each user script/gadget does a explict check if the content was already passed.