These platitudes don't really add anything —which I suspect is one reason they're currently missing— but we're talking about at least three different sorts of message here, each with its own mechanism for being edited:
The ones that are standard to every site. I'm talking about most of the close reasons and the duplicate header. Only SE can alter these and their change would be global.
The custom messages that are specific to us. Elected mods can edit these but they have hard character limits (which links contribute to) and some of the existing messages are already right up against thesethe limit. "We're sorry, but"
We're sorry, but
is 1617 characters we frankly need for actual content. Even if we had the space, adding platitudes would put them out of kilter with the other messages.Pro-forma comments are external from SE and can be edited and customised how you like... But they aren't controlled by moderators or SE, so aren't really relevant here on Meta. File a bug against the project.
I'm not against softening the language but it could be detrimental unless all three areas change at the same time. Even if we had the space in the custom ones (which we don't) I don't think we want a system where some moderativeofficial notices are happy-clappy while others remain clinical. SE needs to start the process by editing the core messages and the other two can fall in line afterwards.
The pro-forma comments are a little different (because they're sent by a person directly). They might also be a good first fiddle to lead the charge on nicer comments.