Usability: When switching through tabs with 3 and 4, do not focus forms
When switching through tabs with the keys 3 and 4, and you encounter one that has currently a form on focus (say, Google), all further 3s and 4s go into that form and your journey comes to an unwanted end. So I think that forms should be unfocused when cycling through tabs with those keys. I also guess that it'd hardly do any harm, because when one switches to another tab, one hardly expects it to have a form on focus, so there would be no workflow interruption through this. Sorry if this isn't new, but 'tabs' and 'forms' are impossible to query for in a section named 'All platforms'.
Are you sure?
I think it is quite well possible to ignore focussed fields for input if and only if you land on a page after pressing 1/2/3/4; not before the first press, of course. With a proper implementation, nothing should get distorted. This should at least become an option, imo.
Agreed. Just like spatial navigation shouldn't automatically enter form fields (which capture subsequent shift+arrow presses), it should pre-focus those fields instead, so you can enter them with Enter if desired. This is also slightly comparable with cycling through the preferences with shift+tab. Stand baffled as you realize that this sets all keyboard shortcuts to "shift+tab" 8-| Or those sites that use constructs like onfocus=this.blur on links, which old Opera also guarded against.
In short: keyboard navigation should only navigate, never change contents or get captured.