When you open chat, you'll notice this small, one pixel wide gray bar. It only appears when chat is open. If chat is just "going by" while you are playing in-game, it is not there. It was not there before 1.9. See attached images.
MC-98982
[Resolved] Small gray bar on left side of open chat
Resolved
Works As Intended
0
Could you be more specific about where this is?
Do both images have it? Because I see something like what you're talking about in the 21.36.34 one, except that's just the box around the grass showing though.