Ignore
 

I was just thinking, perhaps players should not be able to ignore Admin PMs? They might miss certain crucial information.

We have Admin Message for this kind of announcements.

Allow me to rephrase:
They might miss information that the Admins would like them to have, but does not necessarily categorize into the crucial-to-gameplay section.

Like stuff from the NPC server, or masses from the admin (and if that staff member does not have the right to do admin messages)
Yeah, it's a good idea

Staff Mass Messages by-pass the "Ignore Mass Messages" anyway. If they're in the server options, all their mass messages can be read regardless of if you're ignoring mass messages or not