EDIT: @mindbleach@sh.itjust.works shared something that might help to circumvent this shit:
Contained in these parentheses is a zero-width joiner: ()
Basically, add those to whatever you feel that might be filtered out, then remove the parentheses. The content inside the parentheses is invisible, but it screws with regex rules.
left side: logged in. exists.
right side: private window, not logged in. does not exist.
Interesting trick I should save for future use.