IANAD, but bottom left on a page seems easy to miss. I typically want to reload when I see this notification because it makes it more likely that my comments/conversation are relevant to the most recent state of the thing; it seems like a bar across the top would not be too much for this.
We'll take this into consideration and keep an eye open for other feedback, but haven't previously seen other feedback in this vein that I can recall and I think most users find this element fairly visible (e.g., T11141 calls a variant of it "an annoying ... prompt", which suggests it's visible enough to be annoying).
We've also been moving away from global bars (we recently turned the global setup warning bar into a menu item instead, in D16461). Among other reasons, this is partly because they tend to interact negatively with full-page applications like Workboards and Conpherence. See also T1591, which interacts negatively here on two fronts (difficulty/complexity of building global headers which work in all cases; proposes a header which would frequently interact negatively with this one). If we did try to improve the visibility of this notification, I think it is unlikely we'd use a header bar.
If you haven't, you can configure desktop notifications in Settings → Desktop Notifications to improve the visibility of application notifications, although desktop notifications aren't tied to a particular window.
We'll support playing lots of sounds all the time at some point too (T7567) and could maybe accompany this notification with an appropriate audio cue (e.g., a flock of ducks quacking).
We'll take this into consideration and keep an eye open for other feedback,
That said, T11141 and D16461 might not be the best counterexamples: the first is annoying (in my reading of that task) because it follows you around the site; the second is displaying a list of items and a menu item does seem better for that.
I'm also not quite following the "full-page application" point -- I'm only suggesting that the current floating yellow "beeper" notification on the bottom left of the page in Differential be changed to a wider floating yellow bar at the top of the page, where your eye is more likely to be drawn to it. [I guess you're thinking of changing *all* notifications and the consequences of that? I would not want that either]
I have desktop notifications, but they won't quite work for this because, as you say, they aren't tied to a window, and I'd argue they are intended for when you aren't looking at the window/tab; the "reload this page" notification is more relevant to when you are looking at the window.
All notifications currently show up in the same place, so I think the consistency here is better than something new. I'd be more apt to try new treatments in general vs. moving it. We'll probably need to revisit "something on the page changes" UI if we ever build realtime workboards.