Adding this for documentation: I think it might be related to language settings. i'm a chronic tweaker of settings, and i switched my language from English to Undetermined recently. Evidently this hit the filters in a weird way, and hid every post where i had specifically set the language to English. I thought it was supposed to work the other way around, sooooo...idk one mystery solved and another opened up?
Edit: to clarify - setting my language to English caused the missing posts to reappear for me, and it did NOT hide the posts where language was set to Undetermined. Setting my profile language to Undetermined hid all of the English posts, but the Undetermined language posts remained visible. Is this intended behavior? If so, the warning message you get when changing language on the profile screen is inaccurate. Idk if that's something the admins have control over, but just putting it out there.