Yep, the fading is intentional. Just a little stylish thing I threw in just for the lavender theme.
When it does disappear, it should transition to 0 opacity, although it's possible the transition is happning too quickly. Again, this is a lavender trait. In vanilla, there is no flair, just the keyboard (to maximize themability)
As for reloading the page, yes... NodeBB polls to see whether the composer is actually open, every 10 seconds.