Cursor UP doesn't work as expected in mobile site.
Post something and overfill the visible portion of the REPLY Text BOX.
Hit a down arrow.
It moves to a button.
When you now go backwards, it fills the text box from the top again, thus your not where you were,
The UP Arrow acts as a back scroll through the text box and I think it should save the Start position when it leaves, so when the arrow acts as a back key, your cursor is positioned where you were before.
Suppose the box had five visible lines and 2 invisible ones.
1:
2:
3:
4:
5:
6i
7i
<some button - probably reply>
So, the forward arrow does 1,2,3,4,5,6i,7i, and then <some button> and then the <cursor up> makes lines 1-5 visible.
I think it should make lines 3,4,5,6i,7i visible.
It's really annoying when you hit the cursor down too many times,