@smurfworth The navigation bar is sticky on all platforms (certainly all compliant platforms, anyway). You say this results in you having about 1cm of reading space left on your mobile; what's the handset/browser? Any chance of a screen-grab?
I'm not being funny, but unless there's something wildly different on your mobile devices to the couple I've tried (and just tried again) on, your not liking the change to colours and font weight in the header are probably your least picky observation!
The header navigation/menu is sticky because by definition, it provides a header with navigation for the site - being as we thought (and as far as our testing indicated), that it didn't eat-up too much screen real estate on any platform (I'm viewing in Firefox on a 13" laptop at the moment, and I wouldn't describe it as obtrusive; nor is it when I browse in the stock browser on a Galaxy S4 or tablet) - if there's an issue of it leaving such a small amount of space as you describe, we'll look at it again. Actually it was not-'sticky' for a while yesterday only while scripts were shuffled-around.
"why?" "stupid" button? You're sure these are the objective concerns? Why? Again, because we thought it was useful without much of an overhead - it fades in & out so it's there for those who want to use it, and for those who don't like looking at it, it disappears when the page settles. I'd perhaps have said we could look at hiding it for certain mobile devices, but since we're showing more posts per page now (as other requests), I can see how it might be handy. If you can demonstrate to me that it really is more trouble than it's worth, we'll look at that again too.
[For anyone reading who's noticed it] It has been pointed out that perhaps the behaviour of smilies in the reply box on mobile devices isn't ideal; I agree it might take some tweaking, so we'll have a look at that.
Cheers,
Rob.