tl;dr: I'd like to argue that a user who executes the archive action has seen the email in question, and that executing this action means that the email is no longer "new… (read more)
tl;dr: I'd like to argue that a user who executes the archive action has seen the email in question, and that executing this action means that the email is no longer "newly downloaded" and doesn't deserve the highest of visual markings anymore.
We're not talking about the read/unread bit here (the green dot and the grey numbers in the folder pane). We're talking about the "newly downloaded" aka. "new and unseen" bit (the yellow star/rhombus and the blue numbers in the folder pane).
When a new email arrives, it's marked as "newly downloaded" and the inbox lights up blue because of it. Fair enough. It's also unread, of course.
I often archive emails right away without opening/reading them. But I have seen the subject line of course, and I have a pretty good idea of what the email is and why I don't read it.
I have the message pane disabled, so I can easily select an email without it being displayed and being marked as read. In the past, I used the message pane combined with that "mark as read after 1min" setting.
Now when I archive the message, the archive folder lights up blue and when I go in there, the email that I just archived has a star/rhombus. But I don't want my archive folder to look interesting with a blue color only because I just moved an email into it. All the blue colors are supposed to be for things I haven't seen yet and still need to look at. In fact, any email I move to a place should not be able to make that place look blue. Blue color should be for things that appeared for other reasons.
I'm aware that switching folders (e.g. away from inbox and back to it) or restarting Thunderbird will clear this "newly downloaded" bit. But I'm not doing that. I stay in the inbox, I get emails, I read them or archive them immediately. And when a folder on the left lights up in blue (that can happen thanks to my filter rules), then I take a look at that one as well. My Thunderbird application runs for weeks.