GREETINGS from airline maintenance land (though I'm not with UA).
NO, that is not against FAA regs. It's even deferable for, I think, 120 days, though I'd have to look that up.
And, in fact, it's not even broken. Lots of window shades of that particular design/generation do that. You can actually fix it yourself; it's only held in by two tabs along the top and bottom edges.
Just push, and SNAP! It's fixed.
Not that I'd expect a passenger to do that.
But when I see it, I do fix it myself. And then I get the satisfaction/piety/snootiness of having "left it better than I found it"!
That said, I really wish passengers would be a bit kinder to window shades. And other cabin fittings. But that's a gripe for another thread...